Patients with chronic hypertension are at increased risk for obstetric complications, most likely due to higher systemic vascular resistance, which causes decreased placental perfusion.

• Common maternal complications include superimposed preeclampsia (eg, sudden worsening of hypertension, new end-organ damage), abruptio placentae, postpartum hemorrhage, and maternal mortality (eg, stroke).

• Fetal complications include fetal growth restriction with or without oligohydramnios (due to less oxygen/nutrient delivery by the placenta), intrauterine fetal demise, and perinatal mortality.

Because these complications commonly occur prior to 37 weeks gestation, preterm delivery is often required because the high risk for maternal-fetal mortality (eg, intrauterine fetal demise) outweighs the relatively lower risks of fetal prematurity (eg, neonatal respiratory distress syndrome) associated with preterm birth.  In addition, patients with chronic hypertension are also at higher risk for cesarean delivery due to greater rates of sudden-onset maternal instability (eg, superimposed preeclampsia, abruptio placentae) or fetal compromise necessitating expedited delivery.

(Choice A)  Common risk factors for fetal macrosomia (birth weight ≥4500 g) include maternal diabetes mellitus (particularly poorly controlled), multiparity, and a prior macrosomic infant, which are not present in this patient.  In contrast, patients with chronic hypertension are at increased risk for fetal growth restriction (ie, estimated fetal weight <10th percentile).

(Choice B)  Neural tube defects likely occur due to inadequate maternal folate levels.  This patient takes a daily prenatal vitamin for folate supplementation, making this complication less likely.  Hypertension does not increase the risk of neural tube defects.

(Choice C)  Placenta accreta occurs when the placental villi attach to the myometrium rather than the uterine decidua.  The most common risk factor is prior uterine surgery (eg, cesarean delivery, myomectomy), which is not present in this patient.

(Choice D)  Polyhydramnios is associated with poorly controlled diabetes mellitus and/or anomalies that obstruct the fetal intestinal tract (eg, esophageal atresia) and prevent fetal swallowing of amniotic fluid.  In contrast, chronic hypertension is associated with fetal oligohydramnios.

(Choice F)  Preterm prelabor rupture of membranes (PPROM) is the rupture of membranes prior to the onset of labor at <37 weeks gestation.  The most common risk factors for PPROM are genital tract infection and a history of PPROM.  Hypertension is not a risk factor.

Educational objective:
Pregnant patients with chronic hypertension are at increased risk for obstetric complications, including superimposed preeclampsia, fetal growth restriction, and preterm delivery.