209. Abnormal Pregnancy

Question 1

How is perinatal mortality defined and how is US doing?

What is preterm birth? Etiologies (2 groups)

Answer 1

Perinatal mortality: in first 28 days of life + fetal mortality, US rates decreasing but at slower pace than other industrialized countries

PTB: <37 wks GA, accounts for 85% perinatal mortality/morbidity
E: spontaneous (preterm PROM, PTL, cervical insufficiency), iatrogenic (placenta abnormalities - placenta/vasa previa, placental abruption; FGR; pre-eclampsia; isoimmunization

Question 2

Pre-Term Labor

• what is it
• mechanisms
• prevention (meds!)
• mgmt

Answer 2

uterine contractions assoc with cervical dilation <37wks
mech: uterine overdistention, LESS P ACTION, cervical disease, stress, infection, vascular disorder

Prevention: 17-OHP (given for hx of prior PTL), contraception to prolong inter-pregnancy interval, smoking cessation, tx asx bactiuria, tx sx EVC, single embryo transfer

Mgmt: Steroids = fetal benefit for maturation
Tocolysis - block uterine contractions (short term)
PCN for GBS prophylaxis
Mg for fetal neuroprotection

Question 3

Cervical Insufficiency

• what is it
• RFs
• normal cervical maturation
• tx

Answer 3

Incompetent cervix, painless dilation w/o contractions, usually occurs midtrimester
RF: prior hx CI, multiple gestation, EDS (c.t. disorders)
Normal maturation: softening (0-32wks), ripening (32-38wks), dilation (delivery), repair

Tx: Cerclage - suture cervix closed
contraindications: contractions/labor, PPROM (cannot protect fetus), infection, fetal demise, major fetal anomaly

Question 4

Preterm Premature Rupture of Membranes (PPROM)

• what is it
• contributing mechanisms
• dx
• mgmt

Answer 4

rupture of membranes prior to labor onset <37 wks
Contributors: alteration in cervical stromal composition OR induction of amniotic membrane matrix metalloproteases (weaken membrane)

Dx: Sterile speculum exam: see vaginal pooling, basic fluid pH (normally acidic), microscopic ferning pattern (crystallized salt of amniotic fluid)

Mgmt:
<34 weeks: expectant mgmt - ABx (decrease infection risk), steroids (anticipate PTL), fetal surveillance
Contraindications: labor, significant vaginal bleeding (sign of placental abruption), infection (dangerous for maternal/fetal health)
>34 weeks: delivery (PTB)

Question 5

Placental Anomalies
Define the following:
- Placenta Previa (sx, RF, mgmt, complications)
- Placenta Accreta (+ 2 other types)
- Vasa Previa (sx, dx, tx)
- Placental Abruption (sx, RF, mgmt)

Answer 5

Placenta Previa: implantation of placenta covering cervical os

• sx: painless bright red vaginal bleeding, usually 3rd trimester
• RF: prior C section/placenta previa, multiparity, multigestation, advanced maternal age, smoking
• mgmt: pelvic rest (avoid causing bleeds), antenatal steroids, planned C section at 37 weeks GA (deliver before if significant bleeding)

Placenta Accreta: placenta abnormally invades myometrium (no endometrial separation)
Increta: invades 50% myometrium
Percreta: invades myometrium, serosa, surrounding organs

Vasa Previa: fetal vessel transverses cervical os

• sx: vaginal bleeding from fetal blood
• dx: prenatal US, APT TEST (FETAL HB RESISTANT TO LYSIS BY ALKALINE SOLUTION - does not turn green)
• tx: crash C-section

Placental Abruption: premature separation of placenta from uterine wall

• sx: vaginal bleeding with uterine contractions
• RF: HYPERTENSION (most common), prior abruption, abd trauma, PPROM, submucosal fibroids, smoking, cocaine
• mgmt: antenatal steroids (anticipate PTB), delivery based on maternal and fetal status

Question 6

Fetal Growth Restriction (FGR)

- define, cause, dx, mgmt

Answer 6

fetus <10th %ile for given GA
Cause:
Fetal: aneuploidy, anomalies, TORCH infection, multiple gestation
Placental: uteroplacental insufficiency (inadequate perfusion)
Maternal: malnutrition, durg use, smoking, medical conditions
Most common cause: constitutionally small fetus (NORMAL)

Dx: suspected size < expected on fundal height measurements
GOLD STANDARD: US

Mgmt: antenatal steroids and surveillance

Question 7

Pre-eclampsia

• define
• what marks severe preeclampsia
• mechanism
• mgmt

Answer 7

New onset HTN with proteinuria
Severe: BP > 160/110, maternal HA/vision change/RUQ pain, hepatic injury/failure, renal dysfx/failure, pulm edema, coagulopathy, HELLP SYNDROME (hemolysis, elevated liver enzymes, low platelets), eclampsia (seizures)

Mechanism
Normal: placental trophoblasts need to remodel spiral arteries to make them less muscular = less VS = more perfusion
Preeclampsia: non-transformed spiral artery = thick, tortuous muscular = less perfusion/patency = placental ischemia = B cell activation = inflammatory cytokines = high endothelin-1, ROS, sFlt-1 = maternal HTN

Mgmt: Definitive tx: DELIVERY
Balance prematurity risk with risk to maternal/fetal health
control BPs
Prevent eclampsia: MgSO4 (neuroprotective, less seizure risk)

Question 8

Isoimmunization

• define
• prevention
• mgmt

Answer 8

Exposure of Rh- mother to Rh+ fetal blood (disruption of maternal-fetal interface)
Maternal production of Ab’s against D antigen = complications only occur in subsequent Rh+ pregnancies (need developed Abs) = cause fetal anemia

Prevention: give Rh-Ig to ALL pregnant women who are Rh- (unless certain father is Rh-), given at 28wks (high risk time of placental detachment), after delivery, and concerns for breakage in maternal-fetal barrier (bleeding, amniocentesis)

Mgmt:

• paternal phenotype/genotype (no worry if dad Rh-)
• fetal antigen status - amniocentesis vs cell free DNA to check if Rh+
• serial Ab titers (1:32 = risk of anemia)
• fetal middle cerebral artery doppler peak velocity: HIGHER velocity = BAD = lower fetal Hb due to VD (preserve flow) and less viscosity with less RBC mass
• periumbilical cord blood sampling with intrauterine transfusion (infuse adult RBCs to fetus)

Question 9

Spontaneous Abortion

• define
• incidence
• etiologies (4)
• CP

Answer 9

Pregnancy loss <20wks GA
incidence: up to 25% all pregnancies (decreases with increasing GA)
E: Ch abnormalities, congenital anomalies, uterine anomaly, infection, maternal medical comorbidities
CP: vaginal bleeding, pelvic pain, incidental US finding (absence of fetal HR)

Question 10

Stillbirth

• define
• incidence
• etiologies (6)

Answer 10

Intrauterine fetal demise, pregnancy loss >20 wks GA
incidence: 6/1000 births (rarer than spontaneous abortion)
E: Ch abnormalities, congenital anomalies, maternal medical comorbidities, infection, HTN disorders of pregnancy (preeclampsia), multiple gestation