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First aid in OBS & Gyn

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First aid in OBS & Gyn

Post by mandible on Fri Jul 02, 2010 12:02 am

Be on Time
Most OB/GYN teams begin rounding between 6 and 7 A.M. If you are expected
to “pre-round,” you should give yourself at least 10 minutes per patient that
you are following to see the patient and learn about the events that occurred
overnight. Like all working professionals, you will face occasional obstacles to
punctuality, but make sure this is occasional. When you first start a rotation,
try to show up at least 15 minutes early until you get the routine figured out.
Dress in a Professional Manner
Even if the resident wears scrubs and the attending wears stiletto heels, you
must dress in a professional, conservative manner. Wear a short white coat
over your clothes unless discouraged (as in pediatrics).
Men should wear long pants, with cuffs covering the ankle, a long collared
shirt, and a tie. No jeans, no sneakers, no short-sleeved shirts.
Women should wear long pants or knee-length skirt, blouse or dressy
sweater. No jeans, no sneakers, no heels greater than 11⁄2 inches, no opentoed
Both men and women may wear scrubs occasionally, during overnight
call or in the operating room or birthing ward. Do not make this your uniform.
Act in a Pleasant Manner
The rotation is often difficult, stressful, and tiring. Smooth out your experience
by being nice to be around. Smile a lot and learn everyone’s name. If you
do not understand or disagree with a treatment plan or diagnosis, do not
“challenge.” Instead, say “I’m sorry, I don’t quite understand, could you please
explain . . .”
Try to look interested to attendings and residents. Sometimes this stuff is boring,
or sometimes you’re not in the mood, but when someone is trying to
teach you something, look grateful and not tortured.
Always treat patients professionally and with respect. This is crucial to practicing
good medicine, but on a less important level if a resident or attending
spots you being impolite or unprofessional, it will damage your grade and evaluation
quicker than any dumb answer on rounds ever could. And be nice to
the nurses. Really nice. Learn names; bring back pens and food from pharmaceutical
lunches and give them out. If they like you, they can make your life a
lot easier and make you look good in front of the residents and attendings.
Be Aware of the Hierarchy
The way in which this will affect you will vary from hospital to hospital and
team to team, but it is always present to some degree. In general, address your
questions regarding ward functioning to interns or residents. Address your
medical questions to attendings; make an effort to be somewhat informed on
your subject prior to asking attendings medical questions. But please don’t ask
a question just to transparently show off what you know. It’s annoying to
everyone. Show off by seeming interested and asking real questions that you
have when they come up.
Address Patients and Staff in a Respectful Way
Address patients as Sir or Ma’am, or Mr., Mrs., or Miss. Try not to address patients
as “honey,” “sweetie,” and the like. Although you may feel these names
are friendly, patients will think you have forgotten their name, that you are
being inappropriately familiar, or both. Address all physicians as “doctor,” unless
told otherwise.
Be Helpful to Your Residents
That involves taking responsibility for patients that you’ve been assigned to,
and even for some that you haven’t. If you’ve been assigned to a patient, know
everything there is to know about her, her history, test results, details about
her medical problems, and prognosis. Keep your interns or residents informed
of new developments that they might not be aware of, and ask them for any
updates as well.
If you have the opportunity to make a resident look good, take it. If some new
complication comes up with a patient, tell the resident about it before the attending
gets a chance to grill the resident on it. And don’t hesitate to give
credit to a resident for some great teaching in front of an attending. These
things make the resident’s life easier, and he or she will be grateful and the rewards
will come your way.
Volunteer to do things that will help out. So what if you have to run to the
lab to follow up on a stat H&H. It helps everybody out, and it is appreciated.
Observe and anticipate. If a resident is always hunting around for some tape
to do a dressing change every time you round on a particular patient, get some
tape ahead of time.
Respect Patients’ Rights
1. All patients have the right to have their personal medical information
kept private. This means do not discuss the patient’s information with
family members without that patient’s consent and do not discuss any
patient in hallways, elevators, or cafeterias.
2. All patients have the right to refuse treatment. This means they can
refuse treatment by a specific individual (you, the medical student) or
of a specific type (no nasogastric tube). Patients can even refuse lifesaving
treatment. The only exceptions to this rule are a patient who is
deemed to not have the capacity to make decisions or understand situations—
in which case a health care proxy should be sought—or a patient
who is suicidal or homicidal.
3. All patients should be informed of the right to seek advanced directives
on admission. This is often done by the admissions staff, in a
booklet. If your patient is chronically ill or has a life-threatening illness,
address the subject of advanced directives with the assistance of
your attending.
More Volunteering
Be self-propelled, self-motivated. Volunteer to help with a procedure or a difficult
task. Volunteer to give a 20-minute talk on a topic of your choice. Volunteer
to take additional patients. Volunteer to stay late. The more unpleasant
the task, the better.
Be a Team Player
Help other medical students with their tasks; teach them information you
have learned. Support your supervising intern or resident whenever possible.
Never steal the spotlight, steal a procedure, or make a fellow medical student
look bad.
Be Honest
If you don’t understand, don’t know or didn’t do it, make sure you always say
that. Never say or document information that is false (for example, don’t say
“bowel sounds normal” when you did not listen).
Keep Patient Information Handy
Use a clipboard, notebook, or index cards to keep patient information, including
a miniature history and physical, lab, and test results at hand.
Present Patient Information in an Organized Manner
Here is a template for the “bullet” presentation:
“This is a [age]-year-old [gender] with a history of [major history such as
abdominal surgery, pertinent OB/GYN history] who presented on [date]
with [major symptoms, such as pelvic pain, fever], and was found to have
[working diagnosis]. [Tests done] showed [results]. Yesterday the patient
[state important changes, new plan, new tests, new medications]. This
morning the patient feels [state the patient’s words], and the physical exam
is significant for [state major findings]. Plan is [state plan].
The newly admitted patient generally deserves a longer presentation following
the complete history and physical format (see below).
Some patients have extensive histories. The whole history can and probably
should be present in the admission note, but in ward presentation it is often
too much to absorb. In these cases, it will be very much appreciated by your
team if you can generate a good summary that maintains an accurate picture
of the patient. This usually takes some thought, but it’s worth it.
Document Information in an Organized Manner
A complete medical student initial history and physical is neat, legible, organized,
and usually two to three pages long (see Figure 1-1).
The main advantage to doing the OB/GYN clerkship is that you get to see patients.
The patient is the key to learning, and the source of most satisfaction
and frustration on the wards. One enormously helpful tip is to try to skim this
book before starting your rotation. Starting OB/GYN can make you feel like
you’re in a foreign land, and all that studying the first two years doesn’t help
much. You have to start from scratch in some ways, and it will help enormously
if you can skim through this book before you start. Get some of the
terminology straight, get some of the major points down, and it won’t seem so
Select Your Study Material
We recommend:
 This review book, First Aid for the Clinical Clerkship in Obstetrics & Gynecology
 A full-text online journal database, such as [You must be registered and logged in to see this link.] (subscription
is $99/year for students)
 A small pocket reference book to look up lab values, clinical pathways,
and the like, such as Maxwell Quick Medical Reference (ISBN
0964519119, $7)
 A small book to look up drugs, such as Pocket Pharmacopoeia (Tarascon
Publishers, $
As You See Patients, Note Their Major Symptoms
and Diagnosis for Review
Your reading on the symptom-based topics above should be done with a specific
patient in mind. For example, if a postmenopausal patient comes to the
office with increasing abdominal girth and is thought to have ovarian cancer,
read about ovarian cancer in the review book that night.
Prepare a Talk on a Topic
You may be asked to give a small talk once or twice during your rotation. If
not, you should volunteer! Feel free to choose a topic that is on your list; however,
realize that this may be considered dull by the people who hear the lecture.
The ideal topic is slightly uncommon but not rare. To prepare a talk on a
topic, read about it in a major textbook and a review article not more than
two years old, and then search online or in the library for recent developments
or changes in treatment.
If you have read about your core illnesses and core symptoms, you will know a
great deal about medicine. To study for the clerkship exam, we recommend:
2 to 3 weeks before exam: Read the entire review book, taking notes.
10 days before exam: Read the notes you took during the rotation on
your core content list and the corresponding review book sections.
5 days before exam: Read the entire review book, concentrating on lists
and mnemonics.
2 days before exam: Exercise, eat well, skim the book, and go to bed
1 day before exam: Exercise, eat well, review your notes and the
mnemonics, and go to bed on time. Do not have any caffeine after 2 P.M.
Other helpful studying strategies include:
Study with Friends
Group studying can be very helpful. Other people may point out areas that
you have not studied enough and may help you focus on the goal. If you tend
to get distracted by other people in the room, limit this to less than half of
your study time.
Study in a Bright Room
Find the room in your house or in your library that has the best, brightest
light. This will help prevent you from falling asleep. If you don’t have a bright
light, get a halogen desk lamp or a light that simulates sunlight (not a tanning
Eat Light, Balanced Meals
Make sure your meals are balanced, with lean protein, fruits and vegetables,
and fiber. A high-sugar, high-carbohydrate meal will give you an initial burst
of energy for 1 to 2 hours, but then you’ll drop.
Take Practice Exams
The point of practice exams is not so much the content that is contained in
the questions but the training of sitting still for 3 hours and trying to pick the
best answer for each and every question.
Tips for Answering Questions
All questions are intended to have one best answer. When answering questions,
follow these guidelines:
Read the answers first. For all questions longer than two sentences, reading
the answers first can help you sift through the question for the key information.
Look for the words “EXCEPT,” “MOST,” “LEAST,” “NOT,”
RECT,” “ALWAYS,” and “NEVER.” If you find one of these words, circle
or underline it for later comparison with the answer.
Evaluate each answer as being either true or false. Example:
Which of the following is least likely to be associated with pelvic pain?
A. endometriosis T
B. ectopic pregnancy T
C. ovarian cancer ? F
D. ovarian torsion T
By comparing the question, noting LEAST, to the answers, “C” is the best answer.
G (gravidity) 3 = total number of pregnancies, including normal and abnormal
intrauterine pregnancies, abortions, ectopic pregnancies, and hydatidiform
moles (Remember, if patient was pregnant with twins, G = 1.)
P (parity) 3 = number of deliveries > 500 grams or ≥ 24 weeks’ gestation,
stillborn (dead) or alive (Remember, if patient was pregnant with twins,
P = 1.)
Ab (abortion) 0 = number of pregnancies that terminate < 24th gestational
week or in which the fetus weighs < 500 grams
LC (living children) 3 = number of successful pregnancy outcomes (Remember,
if patient was pregnant with twins, LC = 2.)
Or use the “TPAL” system if it is used at your medical school:
T = number of term deliveries (3)
P = number of preterm deliveries (0)
A = number of abortions (0)
L = number of living children (3)
Identification: 25 yo G3P2
Estimated gestational age (EGA): 38 5/7 weeks
Last menstrual period (LMP): First day of LMP
Estimated date of confinement: Due date (specify how it was determined)
by LMP or by ____ wk US (Sonograms are most accurate for dating EGA
when done at < 20 weeks.)
Chief complaint (CC): Uterine contractions (UCs) q 7 min since 0100
History of present illness (HPI): 25 yo G3P2 with an intrauterine pregnancy
(IUP) at 38 5/7 wks GA, well dated by LMP (10/13/99) and US at
10 weeks GA, who presented to L&D with CC of uterine contractions q 7
min. Prenatal care (PNC) at Highland Hospital (12 visits, first visit at 7
wks GA), uterine size = to dates, prenatal BP range 100–126/64–83. Problem
list includes H/o + group B Streptococcus (GBS) and a +PPD with subsequent
negative chest x-ray in 5/00. Pt admitted in early active labor
with a vaginal exam (VE) 4/90/−2.
Past Obstetric History
’92 NSVD @ term, wt 3,700 g, no complications
’94 NSVD @ term, wt 3,900 g, postpartum hemorrhage
Allergies: NKDA
Medications: PNV, Fe
Medical Hx: H/o asthma (asymptomatic × 7 yrs), UTI × 1 @ 30 wks s/p
Macrobid 100 mg × 7 d, neg PPD with subsequent neg CXR (5/00)
Surgical Hx: Negative
Social Hx: Negative
Family Hx: Mother—DM II, father—HTN
ROS: Bilateral low back pain
General appearance: Alert and oriented (A&O), no acute distress
Vital signs: T, BP, P, R
HEENT: No scleral icterus, pale conjunctiva
Neck: Thyroid midline, no masses, no lymphadenopathy (LAD)
Lungs: CTA bilaterally
Back: No CVA tenderness
Heart: II/VI SEM
Breasts: No masses, symmetric
Abdomen: Gravid, nontender
Fundal height: 36 cm
Estimated fetal weight (EFW): 3,500 g by Leopold’s
Presentation: Vertex
Extremities: Mild lower extremity edema, nonpitting
Pelvis: Adequate
VE: Dilatation (4 cm)/effacement (90%)/station (−2); sterile speculum
exam (SSE)? (Nitrazine?, Ferning?, Pooling?); membranes intact
US (L&D): Vertex presentation confirmed, anterior placenta, AFI = 13.2
Fetal monitor: Baseline FHR = 150, reactive. Toco = UCs q 5 min
Blood type: A+
Antibody screen: Neg
Rubella: Immune
VDRL: Nonreactive
HIV: See prenatal records
1 hr GTT: 105
3 hr GTT
PPD: + s/p neg CXR
CXR: Neg 5/00
AFP: Neg x 3
Urine: + blood, − protein, − glucose, − nitrite, 2 WBCs
GBS: +
1. Intrauterine pregancy @ 38 5/7 wks GA in early active labor
2. Group B strep +
3. H/o + PPD with subsequent − CXR 5/00
4. H/o UTI @ 30 wks GA, s/p Rx—resolved
5. H/o asthma—stable × 7 yrs, no meds
1. Admit to L&D
2. NPO except ice chips
3. H&H, VDRL, and hold tube
4. D5 LR TRA 125 cc/hr
5. Ampicillin 2 g IV load, then 1 g IV q 4 hrs (for GBS)
6. External fetal monitors (EFMs)
7. Prep and enema
Always sign and date your notes.
NSVD of viable male infant over an intact perineum @ 12:35 P.M., Apgars
8&9, wt 3,654 g without difficulty. Position LOA, bulb suction, nuchal cord ×
1 reducible. Spontaneous delivery of intact 3-vessel cord placenta @ 12:47
P.M., fundal massage and pitocin initiated, fundus firm. 2nd-degree perineal
laceration repaired under local anesthesia with 3-0 vicryl. Estimated blood
loss (EBL) = 450 cc. Mom and baby stable. Doctors: Johnson & Feig.
S: Pt ambulating, voiding, tolerating a regular diet
O: Vitals
Heart: RR without murmurs
Lungs: CTA bilaterally
Breasts: Nonengorged, colostrum expressed bilaterally
Fundus: Firm, mildly tender to palpation, 1 fingerbreadth below umbilicus
Lochia: Moderate amount, rubra
Perineum: Intact, no edema
Extremities: No edema, nontender
Postpartum Hgb: 9.7
A: S/p NSVD, PP day # 1—progressing well, afebrile, stable
P: Continue postpartum care
1. D/c pt home
2. Pelvic rest × 6 weeks
3. Postpartum check in 4 weeks
4. D/c meds: FeSO4 300 mg 1 tab PO tid, #90 (For Hgb < 10; opinions
vary on when to give FE postpartum)
Colace 100 mg 1 tab PO bid PRN no bowel movement, #60
S: Pt c/o abdominal pain, no flatus, minimal ambulation
O: Vitals
I&O (urinary intake and output): Last 8 hrs = 750/695
Heart: RR without murmurs
Lungs: CTA bilaterally
Breasts: Nonengorged, no colostrum expressed
Fundus: Firm, tender to palpation, 1 fingerbreadth above umbilicus; incision
without erythema/edema; C/D/I (clean/dry/intact); normal
abdominal bowel sounds (NABS)
Lochia: Scant, rubra
Perineum: Intact, Foley catheter in place
Extremities: 1+ pitting edema bilateral LEs, nontender
Postpartum Hgb: 11
A: S/p primary low-transverse c/s secondary to arrest of descent, POD # 1−
afebrile, + flatus, stable
P: 1. D/c Foley
2. Strict I&O––Call HO if UO < 120 cc/4 hrs
3. Clear liquid diet
4. Heplock IV once patient tolerates clears
5. Ambulate qid
6. Incentive spirometry 10×/hr
7. Tylenol #3 2 tabs PO q 4 hrs PRN pain
1. D/c patient home
2. Pelvic rest × 4 weeks
3. Incision check in 1 week
4. Discharge meds:
Tylenol #3 1–2 tabs PO q 4 hrs PRN pain, #30
Colace 100 mg 1 tab PO bid, #60
High-Yield Facts
in Obstetrics
Normal Anatomy
Diagnosis of Pregnancy
Physiology of Pregnancy
Medical Conditions and
Infections in Pregnancy
Complications of
Spontaneous Abortion,
Ectopic Pregnancy, and
Fetal Death
Induced Abortion
The vulva consists of the labia majora, labia minora, mons pubis, clitoris,
vestibule of the vagina, vestibular bulb, and the greater vestibular glands. Basically,
it is the external female genitalia (see Figure 2-1).
Blood Supply
From branches of the external and internal pudendal arteries
H I G H - Y I E L D F A C T S I N
Normal Anatomy
FIGURE 2-1. External female genitalia.
(Reproduced, with permission, from Pernoll ML. Handbook of Obstetrics and Gynecology, 10th ed. New York: McGraw-Hill,
2001: 22.)
Medial group of superficial inguinal nodes
Nerve Supply
Anterior parts of vulva: Ilioinguinal nerves and the genital branch of the
genitofemoral nerves
Posterior parts: Perineal nerves and posterior cutaneous nerves of the thigh
Blood Supply
 Vaginal branch of the uterine artery is the primary supply of the
 Middle rectal and inferior vaginal branches of the hypogastric artery
(internal iliac artery) are secondary blood supplies.
Nerve Supply
 Hypogastric plexus—sympathetic innervation
 Pelvic nerve—parasympathetic innervation
Components of the Uterus
 Fundus: Uppermost region of uterus
 Corpus: Body of the uterus
 Cornu: Part of uterus that joins the fallopian tubes
 Cervix: Inferior part of cervix that connects to the vagina via the cervical
 Internal os: Opening of cervix on the uterine side
 External os: Opening of cervix on the vaginal side
Mesometrium: The visceral layer of the peritoneum reflects against the
uterus and forms this outmost layer of the organ (the side that faces the
Myometrium: The smooth muscle layer of uterus. It has three parts:
1. Outer longitudinal
2. Middle oblique
3. Inner longitudinal
Endometrium: The mucosal layer of the uterus, made up of columnar epithelium
14 Normal Anatomy HIGH-YIELD FACTS
Blood Supply
Uterine arteries—arise from internal iliac artery
Ovarian arteries
Nerve Supply
 Superior hypogastric plexus
 Inferior hypogastric plexus
 Common iliac nerves
Broad ligament: Extends from the lateral pelvic wall to the uterus and adnexa.
Contains the fallopian (uterine) tube, round ligament, uterine and
ovarian blood vessels, lymph, utererovaginal nerves, and ureter (see Figure
Round ligament: The remains of the gubernaculum; extends from the
corpus of the uterus down and laterally through the inguinal canal and
terminates in the labia majora.
Cardinal ligament: Extends from the cervix and lateral vagina to the
pelvic wall; functions to support the uterus.
The fallopian tubes extend from the superior lateral aspects of the uterus
through the superior fold of the broad ligament laterally to the ovaries.
FIGURE 2-2. Supporting structures of the pelvic viscera.
(Reproduced, with permission, from Lindarkis NM, Lott S. Digging Up the Bones: Obstetrics and Gynecology. New York:
McGraw-Hill, 1998: 2.)
Parts, from Lateral to Medial
 Infundibulum: The lateralmost part the uterine tube. The free edge is
connected to the fimbriae.
 Ampulla: Widest section
 Isthmus: Narrowest part
 Intramural part: Pierces uterine wall
Blood Supply
From uterine and ovarian arteries
Nerve Supply
Pelvic plexus (autonomic) and ovarian plexus
The ovaries lie on the posterior aspect of the broad ligament, and are attached
to the broad ligament by the mesovarium. They are not covered by peritoneum.
Blood Supply
Ovarian artery, which arises from the aorta at the level of L1. Veins drain into
the vena cava on the right side and the left renal vein on the left.
Nerve Supply
Derived from the aortic plexus
16 HIGH-YIELD FACTS Normal Anatomy
FIGURE 2-3. Fascia of the pelvis.
(Reproduced, with permission, from Lindarkis NM, Lott S. Digging Up the Bones: Obstetris and Gynecology. New York:
McGraw-Hill, 1998: 2.)
Ovaries are covered by tunica albuginea, a fibrous capsule. The tunica albuginea
is covered by germinal epithelium.
18 HIGH-YIELD FACTS Normal Anatomy
The majority of women have amenorrhea from the last menstrual period
(LMP) until after the birth of their baby.
Although not specific to pregnancy, these symptoms may alert the patient to
the fact that she is pregnant:
 Breast enlargement and tenderness from about 6 weeks’ gestational age
 Areolar enlargement and increased pigmentation after 6 weeks’ GA
 Colostrum secretion may begin after 16 weeks’ GA
 Nausea with or without vomiting, from about the date of the missed period
 Urinary frequency, nocturia, and bladder irritability due to increased
bladder circulation and pressure from the enlarging uterus
Some clinical signs can be noted, but may be difficult to quantify:
 Breast enlargement, tension, and venous distention—particularly obvious
in the primigravida
 Bimanual examination reveals a soft, cystic, globular uterus with enlargement
consistent with the duration of pregnancy (see Table 3-1)
 Chadwick’s sign: Bluish discoloration of vagina and cervix, due to congestion
of pelvic vasculature
The beta subunit of human chorionic gonadotropin (hCG) is detected in maternal
serum or urine.
 hCG is a glycoprotein produced by the developing placenta shortly after
H I G H - Y I E L D F A C T S I N
Diagnosis of Pregnancy
Some women experience
vaginal bleeding in
pregnancy, and therefore
fail to recognize their
Nausea and/or vomiting
occurs in approximately
50% of pregnancies, most
notably at 2 to 12 weeks’
GA, and typically in the A.M.
hCG is a glycoprotein
hormone composed of
alpha and beta subunits.
Hyperemesis gravidariumpersistent
vomiting that
results in weight loss,
dehydration, acidosis from
starvation, alkylosis from
loss of HCl in vomitus, and
 A monoclonal antibody to the hCG antigen is utilized → the hCG–
antibody complex is measured qualitatively
Pregnancy tests not only detect hCG produced by the syncytiotrophoblast
cells in the placenta, but also in:
 Hydatidiform mole
 Other germ cell tumors
 Ectopically producing breast cancers and large cell carcinoma of the
 Blood levels become detectably elevated 8 to 10 days after fertilization
(3 to 3.5 weeks after the LMP)
 hCG rises in a geometric fashion during T1, producing different ranges
for each week of gestation:
Duration of Pregnancy Plasma hCG
(from Time of Ovulation) (mU/mL)
1 week 5–50
2 weeks 50–500
3 100–10,000
4 1,000–30,000
5 3,500–115,000
6–8 12,000–270,000
8–12 15,000–220,000
20–40 3,000–15,000
Urine hCG
 Preferred method to recognize normal pregnancy
 Total urine hCG closely parallels plasma concentration
 First morning specimens have less variability in relative concentration
and generally higher levels, improving accuracy
 Assays detecting 25 mU/mL recognize pregnancy with 95% sensitivity
by 1 week after the first missed menstrual period
20 HIGH-YIELD FACTS Diagnosis of Pregnancy
hCG is similar in structure
and function to luteinizing
hormone (the beta subunits
are similar in both
The hCG alpha subunit
is identical to that in
luteinizing hormone (LH),
follicle-stimulating hormone
(FSH), and thyroidstimulating
Plasma hCG levels in early
pregnancy should double
every 48 hours.
TABLE 3-1. Fundal Height During Pregnancy
Weeks Pregnant Fundal Height
12 Barely palpable above pubic symphysis
15 Midpoint between pubic symphysis and umbilicus
20 At the umbilicus
28 6 cm above the umbilicus
32 6 cm below the xyphoid process
36 2 cm below xyphoid process
40 4 cm below xiphoid processa
a Due to engagement and descent of the fetal head, the fundal height at 40 weeks is typically
less than the fundal height at 36 weeks.
 False negatives may occur if:
 The test is performed too early
 The urine is very dilute
 False positives may occur if:
 Proteinuria (confirm with plasma hCG)
 Urinary tract infection (UTI)
Plasma hCG
Used when quantitative information is needed:
 Diagnosing ectopic pregnancy
 Monitoring trophoblastic tumors
 Screening for fetal abnormalities
Do not provide additional information in diagnosing routine pregnancy since
they are positive < 1 week before urine hCG.
Women of reproductive age with:
The electronic Doppler device can detect fetal heart tones as early as 8 weeks’
GA, albeit with difficulty.
Not generally used to diagnose pregnancy, but can do so once a gestation sac
is present within the uterus.
 To confirm an intrauterine pregnancy (if it is suspected to be ectopic)
 To confirm the presence of a fetal heartbeat in a patient with a history
of miscarriage
 To diagnose multiple pregnancy
 To estimate gestational age
 To screen for fetal structural anomalies
Scan dating becomes progressively less accurate and should be utilized only up
to 20 weeks’ GA:
 US measures the size of the fetus, not the gestational age.
 Biologic variation in size increases as gestation advances.
HIGH-YIELD FACTS Diagnosis of Pregnancy
Do not assay for hCG
before a woman has missed
a menstrual period because
of low test sensitivity
before this time.
If FHTs are not auscultated
by 11 weeks’ GA, an
ultrasonic evaluation should
be performed to document
a viable intrauterine
Scan dating is useful up to
20 weeks’ GA when
menstrual data is unreliable
or conflicts with clinical
22 HIGH-YIELD FACTS Diagnosis of Pregnancy
Aldosterone: Enhances Na+ reabsorption at the collecting duct of the
Aneuploidies: Abnormal numbers of chromosomes that may occur as a
consequence of abnormal meiotic division of chromosomes in gamete formation
Antidiuretic hormone (arginine vasopressin): Acts to conserve water by
increasing the permeability of the collecting duct of the kidney
Blastocyst: At the 8- to 16-cell stage, the blastomere develops a central
cavity and becomes a blastocyst. The cells on the outer layer differentiate
to become trophoblasts.
Blastogenic period: The first 4 weeks of human development
Blastomere/morula: In 2 to 4 days after fertilization, a fertilized oocyte
undergoes a series of cellular divisions and becomes a blastomere or
BMI: A calculation that relates patient’s height to weight:
Obese = ≥ 30
Overweight = 25 to 29.9
Norm = 18.5 to 24.9
Does not consider lean body mass or percentage of body fat
Conception: The fertilization of an ovum by sperm
Decidua: The name given to the endometrium or lining of the uterus during
pregnancy and the tissue around the ectopically located fertilized
Embryonic period: Begins with the folding of the embryonic disk (which
is formed from the inner cell mass) in week 2 of development
Erythrocyte sedimentation rate (ESR): A nonspecific laboratory indicator
of infectious disease and inflammatory states. An anticoagulant is
added to a tube of blood, and the distance the red blood cells fall in 1
hour is the rate.
Fetus: The term given to the conceptus after 8 weeks of life; it has a
crown–rump length of 30 mm and a gestational age of 10 weeks. The fetal
period continues until birth.
Gestational age: The time calculated from the last menstrual period and
by convention exceeds the developmental age by 2 weeks
H I G H - Y I E L D F A C T S I N
Physiology of Pregnancy
Oocyte: The primitive ovum before it has completely developed
Primary: The oocyte at the end of the growth period of oogonium and
before the first maturation division has occurred
Secondary: The larger of two oocytes resulting from the first maturation
Oogenesis: Formation and development of the ovum
Oogonium: The primordial cell from which an oocyte originates
Organogenesis: Occurs between 4 and 8 weeks after conception
Polar body: The small cell produced in oogenesis resulting from the divisions
of the primary and secondary oocytes
Preembryonic period: The first 2 weeks after fertilization
Pregenesis: The time period between the formation of germ cells and the
union of sperm and egg
Puerperium: The period of up to 6 weeks after childbirth, during which
the size of the uterus decreases to normal
Residual volume (RV): The volume of gas contained in the lungs after a
maximal expiration
Tidal volume (TV): The volume of air that is inhaled and exhaled during
normal quiet breathing
Total lung capacity (TLC): The volume of gas contained in the lungs after
a maximal inspiration
Vital capacity (VC): The volume of gas that is exhaled from the lungs in
going from TLC to RV
Zona pellucida: Inner, solid, thick membranous envelope of the ovum
(vitelline membrane, zona radiata)
Table 4-1 summarizes maternal physiologic changes during pregnancy.
Total Body Water
Increases by an average of 8.5 L and is composed of:
 Fetal water
 Amniotic fluid
 Placental tissue
 Maternal tissue
 Increased hydration of connective tissue ground substance → laxity and
swelling of connective tissue → changes in joints that mainly occur in
 Generalized swelling → corneal swelling, intraocular pressure changes,
gingival edema, increased vascularity of cranial sinuses, tracheal edema
Energy Requirements
Energy requirements increase gradually from 10 weeks to 36 weeks by 50 to
100 kcal/day. In the final 4 weeks, requirements increase by 300 kcal/day.
24 HIGH-YIELD FACTS Physiology of Pregnancy
Joint changes (i.e., pubic
symphysis) + postural
changes secondary to
change in center of gravity
results in backaches and
other aches that are
common in pregnancy.
If normal prepregnancy
weight: Patient should gain
25 to 35 lbs. during
pregnancy. There should be
little weight. gain in T1 and
most of weight gain in T2
and T3.
Ideal weight gain:
T1: 1.5 to 3 lbs. gained
T2 and T3: 0.8 lbs./wk
HIGH-YIELD FACTS Physiology of Pregnancy
TABLE 4-1. Summary of Changes in the Body During Pregnancy
T3 (28 wks–
T1 T2 term) Term =
(1–14 wks) (14–28 wks) 37–42 wks During Labor 9-Month Period
Body water ↑ by 8.5 L
Energy requirements ↑ by 50–100 ↑ by 300 kcal/d
Body weight ↑ (primarily ↑ (primarily ↑ (primarily ↑ by 25–35 lb
reflects reflects reflects fetal
maternal maternal growth)
growth) growth)
Tidal volume ↑ ↑by 200 mL
Vital capacity ↑ ↑by 100–200 mL
Cardiac output ↑ by 60% ↑ by 30% during ↑
May ↑ further in
` second stage
of labor
Blood pressure (BP) ↓ ↑by 10–20 mm
Hg during each
May ↑ further in
second stage
of labor
Systolic BP ↔
Diastolic BP ↓ ↓by 15 mm Hg ↑ to T1 level
at 16–20 wks
Heart rate ↑ by 10–15%/min ↔
Stroke volume ↑ by 10% ↑ During each
Central venous ↔ ↑of 3–5 mm Hg
pressure during each
Systemic vascular ↓ from pre- ↓↓ from pre- ↑, but not to ↑ with each
resistance pregnancy pregnancy prepregnancy contraction
level level level
Glomerular filtration ↑ ↑to 60% ↑
rate (GFR) above
levels by
16 wks
Renal plasma flow ↑ ↑to 30–50% Peaks at 30 wks ↑
levels by
20 wks
Plasma aldosterone ↑ w/in 2 wks ↑ 3–5 times the ↑ 8–10 times the ↑
of conception nonpregnant nonpregnant
level level
Physiology of Pregnancy HIGH-YIELD FACTS
TABLE 4-1. Summary of Changes in the Body During Pregnancy (continued)
T3 (28 wks–
T1 T2 term) Term =
(1–14 wks) (14–28 wks) 37–42 wks During Labor 9-Month Period
Serum alkaline ↑
Plasma prolactin↑ ↑10–20 times
Cortisol and other ↑ from 12 wks ↑ ↑ ↑ to 3–5 times
corticosteroids nonpregnant
Glucagon ↑
Insulin sensitivity ↑ ↓at 20 wks ↓
Fasting insulin levels ↑ at 20 wks Peak at 32 wks
Plasma volume ↑ ↑ ↑ ↑ by 50%
Red blood cell ↑ ↑ ↑ ↑ by 18–30%
(RBC) mass
Mean corpuscular ↔or ↑ from ↑ from 86–100
volume (MCV) 82–84 fL fL or more
Neutrophils ↑ ↑ ↑ to 30 wks
Erythrocyte ↑ ↑
rate (ESR)
Albumin blood ↓ ↓from 3.5– ↓ by 22%
levels 2.5 g/100 mL
Total globulin ↑ by 0.2 g/100
Total proteins ↓ by 20 wks
from 7–
6 g/100 mL
Thyroxine-binding ↑ (Thyroxineglobulin
levels double)
Total plasma ↓ by 5% ↑ ↑ ↑ by 24–206%
Low-density ↑ by 50–90%
lipoprotein (LDL)
Very low-density Peaks at 36 wks ↑ by 36%
lipoprotein (VLDL)
High-density ↑ by 30% Decreases from ↑ by 10–23%
lipoprotein (HDL) T2
Triglycerides Reach 2–4 times ↑ by 90–570%
level at 36 wks
Lipoprotein (a) ↑ ↑until 22 wks ↓ to nonpregnant ↔
Uterine contractions Begin at 20 wks ↑
 Metabolic modifications begin soon after conception and are most
marked in the second half of pregnancy when fetal growth requirements
 The uterus and placenta require carbohydrate, fat, and amino acids.
The placenta is freely permeable to glucose, which increases availability to fetus.
First 20 Weeks
Insulin sensitivity increases in first half of pregnancy.
 Fasting glucose levels are lower.
 This favors glycogen synthesis and storage, fat deposition, and amino
acid transport into cells.
After 20 weeks
After 20 weeks, insulin resistance develops and plasma insulin levels rise.
 A carbohydrate load produces a rise in plasma insulin 3 to 4 times
greater than in the nonpregnant state, but glucose levels also are higher.
 This reduces maternal utilization of glucose and induces glycogenolysis,
gluconeogenesis, and maternal utilization of lipids as energy source.
 Despite these high and prolonged rises in postprandial plasma glucose,
the fasting level in late pregnancy remains less than nonpregnant levels.
 Plasma concentration of amino acids falls during pregnancy due to hemodilution.
 Urea synthesis is reduced.
 All lipid levels are raised, with the greatest increases being in the
triglyceride-rich component.
 Lipids cross the placenta.
 Hyperlipidemia of pregnancy is not atherogenic, but may unmask a
pathologic hyperlipidemia.
 Early in pregnancy, fat is deposited.
 By midpregnancy, fat is the primary source of maternal energy.
 Postpartum, lipid levels return to normal.
 May take 6 months
 There is an increased turnover of cholesterol from lipoproteins, creating
an increased supply to most tissues and increased supply for steroid production.
 Total cholesterol is raised postpartum in all mothers, but can be reduced
by dieting after delivery.
Triglycerides, very low-density lipoprotein (VLDL), low-density lipoprotein
(LDL), and high-density lipoprotein (HDL) increase during pregnancy.
HIGH-YIELD FACTS Physiology of Pregnancy
Goal in pregnancy is to
increase the availability of
glucose for the fetus, while
the mother utilizes lipids.
Pregnancy is an anabolic
The optimal time to screen
for glucose intolerance/
diabetes mellitus (DM) in
the pregnant female is at
26 to 28 weeks’ GA.
Normal pregnancy is a
hyperlipemic, as well as a
glucosuric, state.
The increase in cholesterol
excretion results in
increased risk of gallstones.
 Plasma levels of phenytoin fall during pregnancy.
 The half-life of caffeine is doubled.
 Antibiotics are cleared more rapidly by the kidney.
Central Nervous System
Syncope may occur from multiple etiologies:
1. Venous pooling in lower extremities → dizziness/light-headedness especially
with abrupt positional changes
2. Dehydration
3. Hypoglycemia
4. Postprandial shunting of blood flow to the stomach
5. Overexertion during exercise
Emotional and psychiatric symptoms may result from:
 Hormonal changes of pregnancy
 Progesterone → tiredness, dyspnea, depression
 Euphoria secondary to endogenous corticosteroids
Respiratory System
Fetal PCO2 must be greater than maternal PCO2; thus, the maternal respiratory
center must be reset. This is done in several ways:
 During pregnancy, progesterone reduces the carbon dioxide threshold at
which the respiratory center is stimulated and increases the respiratory
center sensitivity. This may lead to hyperventilation of pregnancy.
 Tidal volume (TV) increases by 200 mL.
 Vital capacity (VC) increases by 100 to 200 mL.
Cardiovascular System
 Cardiac output (CO) increases by 40% by week 10, due to a 10% increase
in stroke volume and increase in pulse rate by 10 to 15% per
 Generalized enlargement of the heart and enlargement of left ventricle
 Heart is displaced anterolaterally secondary to rise in level of diaphragm
→ alters electrocardiogram (ECG) and may produce changes that
mimic ischemia.
Physical Exam
 At end of T1—both components of S1 become louder, with exaggerated
 After midpregnancy—90% of pregnant women demonstrate a third
heart sound or S3 gallop.
 Systolic ejection murmurs along the left sternal border occur in 96% of
pregnant patients (due to increased flow across aortic and pulmonic
 Diastolic murmurs are never normal, and their presence warrants evaluation
by a cardiologist.
28 HIGH-YIELD FACTS Physiology of Pregnancy
Healthy women must be
treated as potential cardiac
patients during pregnancy
and the puerperium until
functional murmurs resolve
and the cardiovascular
system returns to baseline
During Labor
 CO increases by 30% during each contraction with an increase in
stroke volume, but no increase in heart rate.
Venous dilation results from:
 Relaxation of vascular smooth muscle
 Pressure of enlarging uterus on inferior vena cava and iliac veins
Gastrointestinal System
Reflux esophagitis (heartburn):
 Enlarging uterus displaces the stomach above the esophageal sphincter
and causes increased intragastric pressure.
 Progesterone causes a relative relaxation of the esophageal sphincter.
 There may also be reflux of bile into the stomach due to pyloric incompetence.
 Constipation may occur secondary to progesterone, which relaxes intestinal
smooth muscle and slows peristalsis.
 Increases in size
 Empties more slowly
 Cholestasis, probably due to a hormonal effect since it also occurs in
some users of oral contraceptives (OCs) and hormone replacement
therapy (HRT)
 Hepatic function increases.
 Plasma globulin and fibrinogen concentrations increase.
 Synthetic rate of albumin increases → total albumin mass increases by
19%, plateauing at 28 weeks.
 Velocity of blood flow in hepatic veins decreases.
 Serum alkaline phosphatase increases largely due to placental production
Genitourinary System
 Urinary stasis secondary to decreased ureteral peristalsis and mechanical
uterine compression of the ureter at pelvic brim as pregnancy progresses
 Asymptomatic bacteruria occurs in 5 to 8% of pregnant women.
 Urinary frequency increases:
 During first 3 months of pregnancy due to bladder compression by enlarging
 During last week of pregnancy as the fetal head descends into pelvis
 Physiologic after T1
 Passing urine four times per night is normal
 Fetal movements and insomnia contribute to the nocturia
 Stress incontinence:
 Occurs frequently during normal pregnancy
HIGH-YIELD FACTS Physiology of Pregnancy
Patients with hypertensive
heart disease or cardiac
disease may develop
progressive or sudden
Increased distensibility and
pressure of veins →
predisposition to
development of varicose
veins of legs, vulva,
rectum, and pelvis.
The superior rectal vein is
part of the portal system
and has no valves, hence
the high pressure within the
system is communicated to
the pelvic veins and
produces hemorrhoids.
Decreased GI motility may
be responsible for the
increased absorption of
water, Na+, and other
The increase in cholestasis
plus increase in lipids and
cholesterol lead to higher
incidence of gallstones,
cholecystitis, and biliary
 Due to relaxation of the bladder supports
 The urethra normally elongates during pregnancy, but not in those
who develop stress incontinence.
Bladder tone decreases, but bladder capacity increases progressively during
Ureters undergo progressive dilatation and kinking in > 90% of pregnant
women at ≥ 6 weeks
 Accompanied by a decreased urine flow rate
 Dilatation is greater on right secondary to dextrorotation of the uterus,
and does not extend below the pelvic brim.
 Dilatation is secondary to the physical obstruction by the pregnant
uterus and the effects of pregnancy hormones.
 Ureteric dilatation extends up to the calyces → increased glomerular
size and increased interstitial fluid → enlarged kidneys (length increases
by 1 cm and weight increases by 20%).
 Renal plasma flow increases from T1, reaching 30 to 50% above nonpregnant
levels by 20 weeks. Flow remains elevated until 30 weeks and
then slowly declines to nonpregnant levels postpartum.
 Glomerular filtration rate (GFR) increases soon after conception. It
reaches 60% above nonpregnant level by 16 weeks and remains elevated
for remainder of pregnancy.
Tubular function changes:
 Tubules lose some of their resorptive capacity—amino acids, uric acid,
and glucose are not as completely absorbed in the pregnant female.
 Results in an increase in protein loss of up to 300 mg/24 hr
Renal retention of Na+ results in water retention. Mother and conceptus increase
their Na+ content by 500 to 900 nmol (due to increased reabsorption
by renal tubules).
Plasma volume increases by 50% during pregnancy due to increase in both red
blood cells (RBCs) and plasma, but proportionately more plasma. This results
in hemodilution.
 Greater in multigravids than primigravids
 Greater in multiple pregnancies than in single pregnancies
 Positively correlated with birth weight
 Increase in plasma volume is less in patients with recurrent abortions.
 Advantage of increased circulating volume:
 Helps to compensate for increased blood flow to uterus and kidneys
 Reduces viscosity of blood and increases capillary blood flow
30 HIGH-YIELD FACTS Physiology of Pregnancy
If frequency occurs in
conjunction with dysuria,
hesitancy, flank pain, or
suprapubic pain, the patient
should be evaluated for a
UTI/cystitis +/pyelonephritis.
In pregnancy, the increased
rate of renal clearance →
reduced effective dose of
GFR increases →quantity
of glucose filtered in urine
is greater than in
nonpregnant state →
tubular threshold for
glucose is exceeded →
glycosuria is detected in
50% of pregnant women.
Albumin concentration falls
by 22% despite the
increase in synthetic rate
due to hemodilution.
Bacteruria + urinary stasis
predispose patients to
pyelonephritis, the most
common nonobstetric cause
for hospitalization during
 Circulating RBC mass increases progressively during pregnancy:
 By 18% in women not given Fe supplements
 By 30% in women on Fe supplementation
 Reticulocyte count increases by ≥ 2%.
 Mean corpuscular volume (MCV) usually increases.
 Fetal Hgb (HbF) concentration increases 1 to 2% during pregnancy,
secondary to an increase in the number of RBCs with HbF
Erythrocyte sedimentation rate (ESR):
 Rises early in pregnancy due to the increase in fibrinogen and other
physiologic changes
 An ESR = 100 mm/hr is not uncommon in normal pregnancy.
 Neutrophil count increases in T1 and continues to rise until 30 weeks.
 Neutrophilic metabolic activity and phagocytic function increases.
 Counts remain unchanged, but function is suppressed.
 Platelet reactivity is increased in T2 and T3 and returns to normal at 12
weeks postpartum
 In 8 to 10% of normal pregnancies, the platelet count falls below 150 ×
103 without negative effects on the fetus.
Endocrine System
In general, the endocrine system is modified in the pregnancy state by the addition
of the fetoplacental unit. The fetoplacental unit produces human
chorionic gonadotropin (hCG) and human placental lactogen (hPL) among
other hormones.
 hCG (luteotropic): Coregulates and stimulates adrenal and placental
steroidogenesis. Stimulates fetal testes to secrete testerone. Possesses
thyrotrophic activity.
 hPL (also called human chorionic somatomammotropin [hCS]): Antiinsulin
and growth hormone-like effects → impaired maternal glucose
and free fatty acid release.
Pituitary gland increases in weight and sensitivity.
 Plasma levels rise within a few days postconception.
 At term, levels are 10- to 20-fold higher than nonpregnant state.
HIGH-YIELD FACTS Physiology of Pregnancy
Tubules are presented with
increased quantities of
urine because of the
increased GFR.
Progesterone increases Na+
excretion, but its increase is
balanced by effects of
increased aldosterone,
mineralocorticoids, and
Hemodilution is not due to
a fall in total circulating
An apparent anemia may
be a sign of good
physiologic adaptation to
pregnancy, while an
elevated hemoglobin may
represent pathology (i.e.,
hemoconcentration in
Follicle-Stimulating Hormone
 Blunted response to gonadotropin-releasing hormone (GnRH)
 Shows a progressive decreased response → no response at 3 weeks after
Luteinizing Hormone
 Response to GnRH diminishes and finally disappears.
 Plasma cortisol and other corticosteroids increase progressively from 12
weeks to term and reach 3 to 5 times nonpregnant levels.
 Half-life of plasma cortisol is increased, while its clearance is reduced.
The following changes are thought to be due to the increase in estrogen during
 Increases in size during pregnancy
 Total thyroxine levels and thyroxine-binding globulin increase. The result
is that free thyroxine remains normal and the mother remains euthyroid.
 Parathyroid hormone levels increase in pregnancy, which increases maternal
calcium absorption, to offset maternal losses across the placenta
to the fetus.
 At term, serum parathyroid hormone levels are higher in the mother,
but calcitonin is higher in the fetus. This results in fetal bone deposition.
Concentrations of proteins in maternal serum fall markedly by 20 weeks,
mostly due to a fall in serum albumin. This fall reduces the colloid osmotic
pressure in the plasma → edema in pregnancy.
 Size of islets of Langerhans increases during pregnancy.
 The number of beta cells increases during pregnancy.
 The number of insulin receptor sites increases during pregnancy.
 Serum levels rise during second half of pregnancy, but insulin resistance
increases as well.
 This insulin resistance may be due to presence of hPL, prolactin, or
other pregnancy hormones that have anti-insulin activity.
 Levels are slightly raised in pregnancy, but not as much as insulin levels.
Integumentary System/Skin
Many physiologic changes in the skin can occur during gestation. Some are
believed to result from changes in the hormonal milieu of pregnancy (see
Table 4-2).
32 HIGH-YIELD FACTS Physiology of Pregnancy
The pregnant female is
more susceptible to viral
infections, malaria, and
The fetoplacental unit
produces hCG and hPL.
Pregnancy andcombinations
of estrogen and
progestational agents (i.e.,
OCs and HRT) are the most
frequent causes of melasma
(often called the “mask
of pregnancy”).
Melanocyte-stimulating hormone increases can result in the following:
 Linea nigra: Black line/discoloration of the abdomen that runs from
above the umbilicus to the pubis; may be seen during the latter part of
 Darkening of nipple and areola
 Facial cholasma/melasma: A light- or dark-brown hyperpigmentation
in exposed areas such as the face. More common in persons with brown
or black skin color, who live in sunny areas, and who are taking OCs.
 A suntan acquired in pregnancy lasts longer than usual.
HIGH-YIELD FACTS Physiology of Pregnancy
Frank goiter may develop
due to increased blood flow
and hyperplasia of
follicular tissue.
TABLE 4-2. Pruritic Dermatologic Disorders Unique to Pregnancy
Disease Onset Pruritis Lesions Distribution Incidence Mortality Intervention
Pruritic urticarial T2–T3 Severe Erythematous Abdomen, Common No Topical
papules and urticarial thighs, (0.25–1%) steroids,
plaques of papules buttocks, antipruritic
pregnancy and occasionally drugs
(PUPPP) plaques arms and (hydroxylegs
Papular eruptions T2–T3 Severe Excoriated No area of Uncommon Unlikely Systemic/
(prurigo papules predilection (1:300– topical
gestationis and 1:2,400) corticopapular
steroids, andermatitis)
Pruritis T3 Severe Excoriations Generalized Common Yes Antipruritics,
gravidarum common (1–2%) cholestyramine
Impetigo T3 Minimal Pustules Genitalia, Rare Yes (maternal Systemic
herpetiformis medial sepsis corticothighs,
common) steroids and
umbilicus, antibiotics
breasts, for secaxillae
Herpes gestationis T2– Severe Erythematous Abdomen, Rare Yes Mild—topical
post- papules, extremities, (1:10,000) steroids,
partum vesicles, generalized antihistabullae
More severe—
 Spider nevi are common (branched growths of dilated capillaries on the
 Palmar erythema
Striae on the abdomen, breasts, etc., develop in response to increased circulating
Grow more rapidly during pregnancy
 The rate at which hair is shed is reduced.
 The excess retained hair is often lost in the puerperium, secondary to
maternal emotional stress.
 Vaginal epithelium hypertrophies and quantity of glycogen-containing
cells shed into vagina increase.
 Connective tissue decreases in collagen content and there is an increase
in water content (like the cervix—see below).
 Vagina becomes more acidic (pH = 4 to 5) → hinders growth of most
pathogens and favors growth of yeasts.
 Hypertrophy and hyperplasia of myometrial smooth muscle secondary
 Action of steroid hormones
 Uterine distention and wall thinning with the growing fetus, placenta,
amniotic fluid
 Term uterus weighs 1,100 g with a 20-fold increase in mass (nonpregnant,
parous uterus weighs 70 g).
Round ligament increases in length, muscular content, and diameter:
 During pregnancy, the ligaments may contract spontaneously or in response
to uterine movement.
 In labor, contractions of the ligaments pulls the uterus forward → expulsive
force is directed as much into the pelvis as possible.
 In the nonpregnant state, the uterine artery is most important blood
34 HIGH-YIELD FACTS Physiology of Pregnancy
Parathyroid hormone and
calcitonin do not cross the
hormone, iodide, thyroidreleasing
hormone, and T4
cross the placenta. TSH
does not.
 During pregnancy, the ovarian arteries contribute 20 to 30% of the
blood supply in 70% of women.
 Uterine arteries dilate to 1.5 times their nonpregnant diameter.
 Amount of collagen within cervix is reduced to one third of nonpregnant
 The duration of spontaneous labor is inversely proportional to cervical
collagen concentration at the beginning of dilation.
Accumulation of glycosaminoglycans and increase in water content and vascularity
in the cervix results in softening and cyanosis = characteristic cervix
of gravid female:
 Results in increased compliance to stretch
 This process is called “cervical ripening” and takes place gradually over
the last few weeks of gestation.
 In early T1, squamous epithelium of ectocervix becomes hyperactive,
endocervical glands become hyperplastic, and endocervical epithelium
proliferates and grows out over the ectocervix.
 The resulting secretions within the endocervical canal create the antibacterial
mucous plug of the cervix.
 The uterine isthmus is normally a small region of the uterus that lies between
the uterine corpus and cervix.
 Beginning at 12 weeks of pregnancy, the isthmus enlarges and thins secondary
to hormonal influences of pregnancy and uterine distention.
 During labor, the isthmus expands and is termed the lower uterine segment.
 Ovulation is necessary for normal fertilization to occur:
 The ovum must leave the ovary and be carried into the fallopian tube.
 The unfertilized ovum is surrounded by its zona pellucida.
 This oocyte has completed its first meiotic division and carries its first
polar body.
 Fertilization typically occurs within 24 hours after ovulation in the
third of the fallopian tube adjacent to the ovary (ampulla):
 The sperm penetrates the zona pellucida and fuses its plasma membranes
with those of the ovum.
 The sperm nucleus and other cellular contents enter the egg’s cytoplasm.
 Fertilization signals the ovum to complete meiosis II and to discharge
an additional polar body.
HIGH-YIELD FACTS Physiology of Pregnancy
The uterus is composed of
smooth muscle, whose
myometrial cells contain
estrogen and progesterone
Cervical effacement causes
expulsion of the mucous
plug as the cervical canal is
shortened during labor.
Cervical effacement and
dilation occur in the already
ripened cervix.
 Fertilized ovum remains in the ampulla for 80 hours after follicular rupture
and travels through isthmus of fallopian tube for 10 hours.
 The fertilized egg divides to form a multicellular blastomere.
 The blastomere passes from the fallopian tube into the uterine cavity.
 The embryo develops into a blastocyst as it freely floats in endometrial
cavity 90 to 150 hours after conception (see Table 4-3).
 On day 5 to 6 of development, the blastocyst adheres to the endometrium
with the help of adhesion molecules on the secretory endometrial
 After attachment, the endometrium proliferates around the blastocyst.
 During week 2, cells in the outer cell mass differentiate into trophoblasts.
36 HIGH-YIELD FACTS Physiology of Pregnancy
TABLE 4-3. Embryology
Weeks Embryo Development
1 Early morula; no organ differentiation.
3 Double heart recognized.
4 Initial organogenesis has begun.
6 Genetic sex determined.
8 Sensory organ development and nondifferentiated gonadal development.
Fetal Development
12 Brain configuration rougly complete, internal sex organs now specific, uterus
now no longer bicornuate, and blood forming in marrow. External genitalia
forming (9–12 weeks).
16 Fetus is active now, sex determination by visual inspection (ultrasound) is
possible due to the formed external genitalia. Myelination of nerves, heart
muscle well developed, vagina and anus open, and ischium ossified.
20 Sternum ossifies.
24 Primitive respiratory movements.
28 Nails appear and testes at or below internal inguinal ring.
36 Earlobe soft with little cartilage, testes in inguinal canals, and scrotum small
with few rugae.
40 Earlobes stiffen by thick cartilage, and scrotum well developed.
Reproduced, with permission, from Lindarkis NM, Lott S. Digging Up the Bones: Obstetrics and
Gynecology. New York: McGraw-Hill, 1998: 6.
Human chorionic
gonadotropin (hCG) is
detectable in maternal
serum after implantation
has taken place,
approximately 8 to 11 days
after conception.
(trophoectoderm) are the
precursor cells for the
placenta and membranes.
 A trophoblastic shell forms the initial boundary between the embryo
and the endometrium.
 The trophoblasts nearest the myometrium form the placental disk; the
other trophoblasts form the chorionic membranes.
 The endometrium or lining of the uterus during pregnancy is termed decidua.
 Maternal RBCs may be seen in the trophoblastic lacunae in the second
week postconception.
The Placenta
The placenta continues to adapt over T2 and T3. It is the primary producer
of steroid hormones after 7 weeks’ gestational age.
Flow in the arcuate and radial arteries during normal pregnancy is high with
low resistance (resistance falls after 20 weeks).
Developmental Ages
Postconception Day Tissue/Organ Formation
4 Blastula
7–12 Implantation
13 Primitive streak
16 Neural plate
19–21 First somite
23–25 Closure of anterior neuropore
25–27 Arms bud
Closure of posterior neuropore
28 Legs bud
44 Sexual differentiation
Multiple Gestation (Figure 4-1)
 Division of embryos before differentiation of trophoblast (between days
2 and 3) → 2 chorions, 2 amnions
 Division of embryos after trophoblast differentiation and before amnion
formation (between days 3 and → 1 placenta, 1 chorion, 2 amnions
 Division of embryos after amnion formation (between days 8 and 13)
→ 1 placenta, 1 chorion, 1 amnion
hCG (Human Chorionic Gonadotropin)
Source: Placenta
 Maintains the corpus luteum
 Stimulates adrenal and placental steroidogenesis
HIGH-YIELD FACTS Physiology of Pregnancy
The decidua produces
maternal steroids and
synthesizes proteins that
are related to the
maintenance and protection
of the pregnancy from
immunologic rejection.
38 HIGH-YIELD FACTS Physiology of Pregnancy
ACTH (Adrenocorticotropic Hormone)
Source: Trophoblasts
Function: Stimulates an increase in circulating maternal free cortisol
hPL (Human Placental Lactogen)
Source: Trophoblasts
Function: Antagonizes insulin → maternal glucose intolerance, lipolysis,
and proteolysis
CRH (Corticotropin-Releasing Hormone)
Source: Placental tissue and decidua
Function: Stimulates placental ACTH release and participates in the
surge of fetal glucocorticoids associated with late T3 fetal maturation
FIGURE 4-1. Multiple gestation.
(Reproduced, with permission, from Lindarkis NM, Lott S. Digging Up the Bones: Obstetrics and Gynecology. New York:
McGraw-Hill, 1998: 56.)
Dichorionic Diamnionic (1/3)
Separate development
Dichorionic Diamnionic (1/3)
Fused development
Monoamnionic (rare)
(Siamese twins)
Twins share single cavity
Diamnionic (< 1/3)
Twins are in separate cavities
Dizygotic Twins
Nonidentical or Fraternal Twins
(Always have 2 chorions and 2 amnions,
and sexes may be different.)
Monozygotic Twins
Identical or Maternal Twins
HIGH-YIELD FACTS Physiology of Pregnancy
Source: Decidualized endometrium
Function: Regulates fluid and electrolyte flux through the fetal membranes
Alpha-Fetoprotein (AFP)
Source: Yolk sac, fetal gastrointestinal tract, and fetal liver
Function: Regulates fetal intravascular volume (osmoregulator)
 MSAFP peaks between 10 and 13 weeks’ gestational age, then declines
 Detectable as early as 7 weeks’ gestation
Function: Estrogens affect uterine vasculature, placental steroidogenesis,
and parturition.
 Maternal ovaries for weeks 1 through 6 of gestation
 Subsequently, the placenta secretes increasing quantities of estradiol
synthesized from the conversion of circulating maternal and fetal
 After T1, the placenta is the major source of circulating estradiol.
 Maternal ovaries, adrenals, and peripheral conversion in the first 4 to
6 weeks of pregnancy
 The placenta subsequently secretes increasing quantities.
 Continued production is dependent on the presence of a living fetus.
 Corpus luteum before 6 weeks’ gestational age
 Thereafter, the placenta produces progesterone from circulating maternal
low-density lipoprotein (LDL) cholesterol.
 Affects tubal motility, the endometrium, uterine vasculature, and parturition
 Inhibits T lymphocyte–mediated tissue rejection
Source: Decidual tissue
Function: Suppresses the maternal immune rejection response of the implanted
Amniotic fluid AFP and
maternal serum (MSAFP)
are elevated in association
with neural tube defects
and low in trisomy 21.
MSAFP is decreased in
pregnancies with Down’s
In women with threatened
T1 abortions, estradiol
concentrations are
abnormally low for
gestational age.
During T3, low estradiol
levels are associated with
poor obstetrical outcomes.
Abortion will occur in 80%
of women with
progesterone levels under
10 ng/mL.
LDL Cholesterol
Source: Fetal adrenal gland
 Principal regulatory precursor of corpus luteum progesterone production
 Principal lipoprotein utilized in fetal adrenal steroidogenesis
40 HIGH-YIELD FACTS Physiology of Pregnancy
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Re: First aid in OBS & Gyn

Post by aiwahsh on Wed Mar 09, 2011 4:29 pm

Razz cheers cheers bounce farao

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