OB Study Guide

What is conception through the 8th week of gestation?

Embryo

What is the 9th week of gestation to delivery?

Fetus

What is Primigravida (Primip)?

First pregnancy

What is the Multigravida (Multip)?

2+ pregnancies

What is the fetal demise after 20 weeks gestation?

*early 20-27 wks, late 28-36 wks, term ≥37 wks

Stillbirth

What is a low birth weight?

≤ 2500 g (5 lb 8 oz)

What is a normal birth weight?

2500 - 4500 g

What is a high birth weight (fetal macrosomia)?

≥ 4500 g (8 lbs 13 oz)

What is considered an immature infant?

Completed weeks 20 - <28

What is considered a preterm infant?

Born before 37 weeks

(premature = completed weeks 28 - < 37)

What is considered a post mature infant (post dates)?

Completed 42 weeks

What is considered a full term (mature) infant?

37 - 42 weeks

When can a fetus survive outside of the womb?

22 weeks

What is the MCC of secondary amenorrhea?

Pregnancy

What is the first trimester?

Conception - 12 weeks & 6 days

What is the second trimester?

13 weeks - 27 weeks & 6 days

What is the third trimester?

28 weeks until full delivery

How long does normal human pregnancy last?

280 days / 40 weeks / 10 months

How is the estimated due date (EDD) from LMP calculated?

Nagele’s rule → take the 1st day of LMP, subtract 3 mos, add 7 days and add 1 year

How do you calculate GA from EDD?

[280 - (EDD - reference date)] / 7

What is gravida?

Number of times pregnant, carried to term or not

How many gravidas & paras do twins / multituplets count as?

1

What is Para?

Number of births that occurred after 20 weeks, viable or nonviable

What are the subcategories of Para?

Full term: ≥ 37 wks

Premature birth: 20-36 wks & 6 days

Abortion/miscarriages: < 20 wks

Living children

What is the GPA classification?

Gravida, para, abortus

How are fundal heights calculated?

Measure the distance from the superior edge of the pubic symphysis to the palpable fundus of the uterus (cm w/ soft tape measure)

*heights roughly correlate w/ gestational dates

What is the fundal height from 20 weeks to 36 weeks gestation?

Distance = weeks of gestation +/- 2

(ex: 24 weeks = 24 cm +/- 2cm)

What is the landmark to determine uterine size at 8 weeks?

Palpable at pubic symphysis

What is the landmark to determine uterine size at 12 weeks?

Becomes an abdominal organ

What is the landmark to determine uterine size at 16 weeks?

Midpoint between pubic symphysis and umbilicus

What is the landmark to determine uterine size at 20 weeks?

At umbilicus

What is the landmark to determine uterine size at 26-34 weeks?

Fundal height correlates with GA (± 2)

What is the landmark to determine uterine size at 36-40 weeks?

Decrease in fundal height

What is a normal FHT?

120-160 bpm

If in the 1st trimester, the US dating measures > 1 week difference GA than calculated by LMP, which do you go with?

US

If in the 2nd trimester, the US dating measures > 2 week difference GA than calculated by LMP, which do you go with?

US

If in the 3rd trimester, the US dating measures > 3 week difference GA than calculated by LMP, which do you go with?

US

In general, if there is no difference in GA calculations, should you stick with US or LMP?

LMP

What does a lecithin:sphingomyelin (L:S) ratio of 2:1 indicate?

Lung maturity

What does a L:S ratio of < 2:1 indicate?

Immature lungs → consider maternal steroid injection to decrease risk of of NRDS if in labor

What is one of the last fetal surfactants to develop (≥37 weeks), but is a less reliable indicator of lung maturity if the mother is diabetic or if amniotic fluid is contaminated?

Phosphatidylglycerol (PG) presence

When should the first obstetric US be done?

≥ 6 weeks→ earlier than this may be prior to cardiac development & can’t detect FHT or determine viability

*TV if < 6 wks, TA if > 6 wks

What is the first line RX for syphillis in pregnancy?

PCN

What is the first line RX for chlamydia in pregnancy?

Azithromycin

What is the first line RX for gonorrhea in pregnancy?

Ceftriaxone

What is the first line RX for HSV in pregnancy?

PO suppressive therapy at 35-36 wks; C section if active lesions

What is the first line RX for trichomoniasis in pregnancy?

Metronidazole (category B)

What is the first line RX for candidiasis in pregnancy?

Miconazole cream

What is the first line RX for BV in pregnancy?

Metronidazole (category B) after first trimester

What is used to assess fetal positioning in the 3rd trimester?

Leopold’s maneuvers

When is is nuchal translucency (NT) US screening completed to measure fetus’s nuchal fold thickness?

11-13 wks

> 3.33 mm = soft marker for down syndrome

What is non-invasive prenatal testing/screening (NIPT)?

*blood test- MaterniT21, integrated screening

Screening for chromosomal fetal abnormalities between 10-20 wks

*inaccurate before 10 wks d/t insufficient fetal fraction

What does MaterniT21 evaluate for?

Common trisomies, select microdeletions (22q, 15q), rare sex aneuploidies, & fetal sex

*does NOT evaluate for open neural tube deficits

What is integrated screening?

Combines maternal age risk, 1st trimester NT, & serum PAPP-A w/ 2nd trimester measurements of AFP, uE3, hCG, & DIA

*provides risk assessments for Down syndrome, open spina bifida, & trisomy 18

What has the highest detection rate and lowest false positive rate of detecting pregnancies with Down syndrome?

Integrated screening

When is the maternal serum alpha fetoprotein (AFP) level drawn?

15-21 wks (18 is most accurate)

What protein is produced by the fetal liver & yolk sac & is drawn during the second trimester to look for an increased risk of neural tube defects such as spina bifida?

AFP

In what conditions is the maternal serum AFP increased or decreased?

Elevated in spina bifida

Low in trisomy 18 & 21

When is the fetal anatomy screening by US completed to check fluid levels, growth, viability, & detect anatomic abnormalities suggestive of aneupolides and congenital defects?

18-21 wks (20 preferred)

When is the simple glucose challenge test (GCT) performed to screen for GDM?

24-28 weeks

How is the simple GCT test performed?

Nonfasting pt drinks 50g glucose soln & blood sugar is measured at 1 hr

*positive if > 140 → do a 3 hr GTT

What risks are associated with GDM?

Macrocosmic or LGA (> 9 lbs), birth comps, shoulder dystocia, preterm delivery, still birth, maternal risk of T2DM PP

What test performed at 15-20 wks (not routine) allows for the collection of amniotic fluid to provide a sample of fetal DNA to diagnose potential genetic defects?

*risk of clubfoot if performed before 15 wks

Amniocentesis

When is the US screening completed in the 3rd trimester to help determine final positioning of the fetus?

~ 36 weeks

When should a routine rectovaginal swab culture be performed to check for GBS?

35-37 wks

What is there an increased risk of if a pregnant woman has a GBS infection?

Preterm labor, amnionitis, endometritis, maternal wound infx, & transmission during delivery causing generalize sepsis of the newborn

What is the treatment for GBS in pregnancy?

1st line: PCN

Allergy: need a C&S to guide tx d/t resistance (macrolide)

When is a biophysical profile (BPP) completed in pregnancy?

32 weeks (sometimes earlier) in high risk pregnancy

After 40 wks in normal pregnancy

What does a biophysical profile (BPP) evaluate?

Fetal breathing, gross fetal tones, gross fetal movements, amniotic fluid levels, & NST (fetal HR monitoring w/o stress/contraction)

*each worth 2 pts; 10 pts total

What is a good or reassuring BPP score?

8-10

What BPP score may indicate early delivery and should be retested in 12-24 hours?

6-7

What BPP score is concerning & requires immediate management?

≤ 5

What test utilizes a fetal monitor to measure cardio accelerative response (FHR) in response to fetal movement, and is most reliable after 28-32 wks?

Non-stress test (NST)

What is the criteria for a reactive NST?

Baseline FHR 120-160 bpm

Presence of periodic accelerations (2 accelerations w/in 20 minutes) w/ increases of 15 bpm for 15s

What is the criteria for an abnormal (non-reactive) NST?

Absence of accelerations or presence of sporadic repeated decelerations of FHR

What vaccinations should be AVOIDED in pregnancy?

Live virus or bacterial → MMR, yellow fever, BCG, varicella, oral polio

What vaccines are okay to give in pregnancy?

Tdap (27-36 wks if no UTD), Hep A, Hep B, flu & pneumovax

*use caution w/ inactivated or assembled vaccines

How often should Tdap vaccinations be updated?

Mom: once each pregnancy no matter when the last one was (~ 27-36 wks no UTD)

Anyone of age that will be around the baby after delivery: every 10 yrs

What prenatal vitamins are recommended for pregnancy?

*important for fetal neuro development

400-800 mcg Folate (1 mg if prescription), 40 mg elemental iron, & DHA omega 3

What kind of twin?

• 2 separate chorions & amniotic sacs

• MC w/ fraternal twins

• lowest mortality risk (but still higher than singletons)

• form when spitting takes place by the 3rd day after fertilization

Dichorionic-Diamiotic (DiDi)

What kind of twins?

• share the same placenta, have 2 amniotic sacs

• MC w/ identical twins

• occurs on days 4-8

Monochorionic Diamniotic (MoDi)

What is an increase in saliva production secondary to a placental hormone?

*tx: mints, gum, small frequent meals & sips of water, Nexium

Ptyalism

What condition is characterized by severe/refractory N/V that can lead to dehydration, hypovolemia, electrolyte imbalances, ketosis, weight loss & erosion of enamel?

Hyperemesis Gravidarum

What is the treatment for mild-moderate Hyperemesis Gravidarum (HG)?

PO fluids w/ elytes, ginger, unisom/B6, magnesium (PO/TD), antiemetics - zofran, reglan, promethazine rectal suppository

What is the treatment for moderate-severe HG?

Reglan, promethazine, IV zofran pump & IVFs at home (w/ home nurse)

Hospitalization & IV fluid transfusion if refractory

Low dose prednisolone if severe & not responding to antiemetics

What is the pathophysiology of gallbladder dysfunction associated with pregnancy?

Inc estrogen → inc cholesterol & lecithin → cholesterol supersat & crystallization → Cholelithiasis

Progesteron & relaxin → relaxes SM → less GB contraction → Cholestasis

*both inc risk of cholecystitis & choledocholithiasis

What condition?

• 3rd trimester; d/t increased estrogen & other hormones that reduce bile transport through the liver

• lack of bile salts → dec fat digestion & absorption of fat soluble vitamins

• bile back up in blood → hyperbilirubinemia & maternal & fetal comps

• dx:

  • CMP: elevated LFTs, ALP, total & direct bili

    Bile acids: increased

    PTT: prolonged d/t poor vit K absorption

    GGT: normal

Intrahepatic cholestasis

What sx are associated with intrahepatic cholestasis of pregnancy?

Generalize pruritus worst on palms/soles & at night, secondary insomnia, RUQ pain, N, dec appetite, steatorrhea, encepahlopathy (severe)

What is the treatment for intrahepatic cholestasis of pregnancy?

Ursodeoxycholic acid until delivery; resolves w/ delivery of child

What causes hypercoagulability in pregnancy?

Inc in estrogen, factor VII, fibrinogen, thrombin

Dec in protein S (an anticoagulant)

*inc risk of VT: 2x during pregnancy, 5.5x puerperium

What is peripartum cardiomyopathy?

Specific type of dilated cardiomyopathy when other causes outside of pregnancy can’t be found; MC in mothers > 30 y/o

*may be d/t inc BV, pre-load, & HR

What may be an issue for asthmatics during pregnancy?

Mucosal hyperemia secondary to inc blood volume & overall vasodilation → congestion & inc secretions

How is renal function affected in pregnancy?

Increase: renal plasma flow, GFR, plasma renin, angiotensin, CrCl

Decrease: serum cr, uric acid, & BUN

What does increased GFR in pregnancy cause?

Inc load of glucose in renal tubules → inc glucose excretion

What effect does progesterone have on the bladder during pregnancy?

Dec bladder tone → inc residual volume → dilation of collecting system → increased risk of urinary stasis → increased risk of UTI & pyelonephritis in pts w/ asx bacteriuria

What does the increased amount estrogen and glucose in the urine during pregnancy increase the risk of?

Bacteria overgrowth & UTIs

What bone changes are seen in pregnancy?

Increase: PTH, bone turnover, ALP, (no change in bone density)

Decrease: serum Ca (hemodilution)

In what trimester are headaches common and often due to caffeine withdrawal?

First trimester

Headaches starting in which trimester can be a sign of pre-eclampsia?

Second trimester

What is Chadwicks sign?

Blue discoloration of vulva, vagina, and/or vaginal portion of cervix