A 24-year-old woman, gravida 1 para 0, at 37 weeks gestation comes to the office for a routine prenatal visit. The patient has no concerns today. Her fetus is active, and she has no contractions, vaginal bleeding, or leakage of fluid. The patient's pregnancy was dated by a first-trimester ultrasound, and her 18-week ultrasound revealed normal fetal anatomy. At 26 weeks gestation, her 1-hour glucose screen was abnormal, but her 3-hour glucose tolerance test was normal. The patient has no medical conditions and has had no surgeries. Blood pressure is 112/68 mm Hg and pulse is 90/min. Fundal height is 42 cm and fetal heart rate is 138/min. Because of the uterine size-dates discrepancy, an ultrasound is performed, which reveals an intrauterine fetus in the cephalic position with an amniotic fluid index of 30 cm (normal: 8-24 cm). Which of the following is the best next step in management of this patient?

Question

A 24-year-old woman, gravida 1 para 0, at 37 weeks gestation comes to the office for a routine prenatal visit.  The patient has no concerns today.  Her fetus is active, and she has no contractions, vaginal bleeding, or leakage of fluid.  The patient's pregnancy was dated by a first-trimester ultrasound, and her 18-week ultrasound revealed normal fetal anatomy.  At 26 weeks gestation, her 1-hour glucose screen was abnormal, but her 3-hour glucose tolerance test was normal.  The patient has no medical conditions and has had no surgeries.  Blood pressure is 112/68 mm Hg and pulse is 90/min.  Fundal height is 42 cm and fetal heart rate is 138/min.  Because of the uterine size-dates discrepancy, an ultrasound is performed, which reveals an intrauterine fetus in the cephalic position with an amniotic fluid index of 30 cm (normal: 8-24 cm).  Which of the following is the best next step in management of this patient?

Quizplus · Accepted Answer

Explanation: Fundal height (ie, uterine size) is measured during second- and third-trimester prenatal visits as an indirect assessment of fetal growth and amniotic fluid volume. This patient's uterine size-larger-than-dates discrepancy (42 cm at 37 weeks gestation) prompted an ultrasound evaluation that reveals polyhydramnios, defined as an amniotic fluid index ≥24 cm or a deepest vertical pocket of ≥8 cm. Polyhydramnios occurs due to an imbalance of fluid production (ie, fetal urination) and removal (ie, fetal swallowing). Although some patients have an identifiable cause (eg, diabetes mellitus, fetal tracheoesophageal fistula), most cases are idiopathic, as in this patient. Patients with polyhydramnios may have abdominal discomfort (from increased uterine size), dyspnea (due to maternal lung compression), and preterm contractions (from increased intrauterine pressure); however, most patients are asymptomatic. Management is based on severity, maternal symptoms, and gestational age: Patients with severe or symptomatic polyhydramnios at preterm gestation are at increased risk for obstetric complications, including preterm labor and preterm prelabor rupture of membranes. Therefore, these patients may benefit from amnioreduction (ie, amniotic fluid removal by amniocentesis) (Choice A). In contrast, patients with mild, asymptomatic polyhydramnios at term gestation, such as this patient, can undergo expectant management because obstetric outcomes are unchanged by increased antenatal fetal surveillance or intervention. (Choice B) Betamethasone is administered to patients at risk for preterm delivery (ie, <37 weeks gestation) to reduce the risk of neonatal respiratory distress syndrome. (Choices C and F) In patients with mild, asymptomatic polyhydramnios, delivery planning (eg, cesarean delivery, induction of labor) is based on routine obstetric indications only (eg, nonreassuring fetal heart rate, postterm gestation). (Choice E) Indomethacin is a cyclooxygenase inhibitor that reduces amniotic fluid volume by decreasing prostaglandin synthesis, fetal renal blood flow, and fetal urine output. It is contraindicated in patients at ≥32 weeks gestation due to the risk of premature fetal ductus arteriosus closure. Educational objective: Most cases of polyhydramnios (ie, amniotic fluid index ≥24 cm) are idiopathic and asymptomatic. Patients at term gestation with mild, asymptomatic polyhydramnios are expectantly managed. References: SMFM consult series #46: evaluation and management of polyhydramnios. (http://www.ncbi.nlm.nih.gov/pubmed/30048635) ACOG committee opinion no. 764: medically indicated late-preterm and early-term deliveries. (http://www.ncbi.nlm.nih.gov/pubmed/30681545)

A 24-Year-Old Woman, Gravida 1 Para 0, at 37 Weeks