A 29-year-old woman, gravida 2 para 1, at 41 weeks gestation comes to the office for a routine prenatal visit. The patient has had no abdominal pain, leakage of fluid, or vaginal bleeding. Fetal movement is normal. The patient has had an uncomplicated pregnancy. An anatomy ultrasound at 20 weeks gestation was normal. Group B Streptococcus screening at 37 weeks gestation was negative. Her prior pregnancy ended in a post-term vaginal delivery. The patient has no chronic medical conditions and does not use tobacco, alcohol, or illicit drugs. Blood pressure is 120/70 mm Hg and pulse is 72/min. BMI is 29 kg/m2. Fundal height is 37 cm. Nonstress test shows moderate variability, multiple accelerations, and no decelerations. Ultrasound reveals a fetus in vertex presentation, and the single deepest pocket of amniotic fluid is 1.2 cm. Which of the following is the best next step in management of this patient?
Late- & post-term pregnancy | |
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Patients with late-term (≥41 weeks gestation) and post-term (≥42 weeks gestation) pregnancies are at increased risk for maternal and fetal complications. Maternal complications, such as postpartum hemorrhage and perineal lacerations, are due to increasing fetal growth (ie, macrosomia) associated with increasing gestational age. Fetal complications are due to age-related placental changes (eg, infarctions, calcifications) that result in uteroplacental insufficiency, fetal hypoxemia, and possible intrauterine fetal demise.
Due to the risk of fetal complications, patients with late-/post-term pregnancies undergo fetal monitoring with a nonstress test and amniotic fluid volume to evaluate for uteroplacental insufficiency. Signs of uteroplacental insufficiency include late decelerations on nonstress test and/or oligohydramnios on ultrasound (ie, single deepest pocket <2 cm). Oligohydramnios occurs due to uteroplacental insufficiency because fetal blood is shunted from the kidney (which produces amniotic fluid) to the brain to prevent central nervous system suppression from chronic fetal hypoxemia.
In patients with a late-/post-term pregnancy and oligohydramnios on ultrasound or an abnormal nonstress test, immediate delivery is indicated due to the risk of intrauterine fetal demise. This patient has a reactive nonstress test and vertex presentation and can therefore undergo an induction of labor.
(Choice A) An amnioinfusion is used in the management of variable decelerations, which typically occur secondary to oligohydramnios from rupture of membranes and subsequent fetal cord compression. This patient's oligohydramnios is due to chronic placental insufficiency and has no associated variable decelerations; therefore, amnioinfusion is not indicated.
(Choices B and D) A biophysical profile and contraction stress test are performed to assess fetal well-being. This patient's oligohydramnios complicating a post-term pregnancy, already meets the criteria for delivery; therefore, additional evaluation of fetal well-being is not required as it does not change management.
(Choice C) Cesarean delivery is indicated in patients with abnormal fetal heart tracings (eg, late decelerations) or fetal malpresentation (eg, breech), neither of which is seen in this patient.
(Choice F) Patients with late-/post-term pregnancies and normal amniotic fluid volume (single deepest pocket ≥2 and <8 cm) can continue routine prenatal care until ≥42 weeks gestation.
Educational objective:
Late-/post-term pregnancies are at increased risk for uteroplacental insufficiency and intrauterine fetal demise. Therefore, these patients undergo routine fetal monitoring with a nonstress test and amniotic fluid volume. Patients with oligohydramnios, a marker for placental insufficiency, require immediate delivery.