A 26-year-old primigravid woman at 25 weeks gestation comes to the hospital due to preterm labor. For the last 6 hours, the patient has had intermittent, painful contractions but no vaginal bleeding or leakage of fluid. Blood pressure is 110/66 mm Hg and pulse is 90/min. BMI is 23 kg/m². Cardiopulmonary examination is normal. The uterus is nontender. On sterile speculum examination, the cervix is visibly 2 cm dilated. Fetal heart rate monitoring shows a baseline of 150/min, no decelerations, no accelerations, and minimal variability. Contractions occur every 2-3 minutes on tocodynamometry. The patient is administered indomethacin for tocolysis. This intervention increases this patient's risk for which of the following obstetric complications?

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Explanation: This patient with frequent contractions causing cervical dilation at 25 weeks gestation is in preterm labor. Management of preterm labor depends on gestational age, with increased intervention required at earlier gestations due to the risks of neonatal prematurity. Patients at <32 weeks gestation in preterm labor require: indomethacin to inhibit contractions and delay delivery (ie, tocolysis). betamethasone to promote fetal lung maturity. magnesium sulfate to decrease the risk of cerebral palsy (ie, fetal neuroprotection). penicillin to decrease the risk of neonatal group B Streptococcus infection. Although the benefits typically outweigh the risks, indomethacin tocolysis can have adverse fetal effects. Indomethacin, a nonspecific cyclooxygenase inhibitor, decreases prostaglandin production and leads to fetal vasoconstriction (eg, premature closure of the ductus arteriosus). The subsequent decreased renal perfusion and fetal oliguria can result in oligohydramnios (ie, amniotic fluid index ≤5 cm), particularly with prolonged administration; therefore, patients typically receive indomethacin for ≤48 hours. The oligohydramnios associated with indomethacin use is typically transient and resolves without intervention once the medication is discontinued. (Choice A) Although betamethasone, a corticosteroid, may transiently increase maternal glucose levels, it does not increase the risk of gestational diabetes mellitus (GDM). Indomethacin does not increase the risk of GDM. (Choice B) The risk of intraamniotic infection is increased in patients with preterm prelabor rupture of membranes, but indomethacin does not increase the risk. (Choice D) Risk factors for preeclampsia include chronic hypertension, diabetes mellitus, and multiple gestation but not indomethacin use. (Choice E) The most common cause of pulmonary edema in pregnancy is preeclampsia due to increased vascular permeability and hemodynamic dysfunction. Although indomethacin, like other nonsteroidal anti-inflammatory drugs, can lead to some degree of fluid retention, its use is not associated with pulmonary edema. Educational objective: Indomethacin tocolysis (ie, to inhibit contractions) is indicated in patients with preterm labor at <32 weeks gestation. Indomethacin tocolysis can cause oligohydramnios and premature closure of the fetal ductus arteriosus, although its benefits typically outweigh these risks. References: Practice bulletin no. 171: management of preterm labor. (http://www.ncbi.nlm.nih.gov/pubmed/27661654) Tocolytic therapy for acute preterm labor. (http://www.ncbi.nlm.nih.gov/pubmed/22370109) Cyclo-oxygenase (COX) inhibitors for treating preterm labour. (http://www.ncbi.nlm.nih.gov/pubmed/26042617)

A 26-Year-Old Primigravid Woman at 25 Weeks Gestation Comes to the Hospital