A 29-year-old woman, gravida 2 para 1, at 12 weeks gestation comes to the office for an initial prenatal visit. The patient has had no nausea, abdominal pain, or vaginal bleeding. Her first pregnancy ended in an operative vaginal delivery after induction of labor at 42 weeks gestation. She has no chronic medical conditions and has had no surgeries. The patient takes a daily prenatal vitamin and does not use tobacco, alcohol, or illicit drugs. Blood pressure is 118/74 mm Hg and pulse is 76/min. BMI is 27 kg/m². The uterine fundus is 2 cm below the umbilicus. Pelvic examination is normal. Ultrasound shows an intrauterine 12-week twin gestation with 2 posterior-fundal placentas. The fetal heart rates are normal. Compared to patients with singleton gestations, this patient is at increased risk for which of the following obstetric-related complications?

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Explanation: 11ec25c8_da4b_a46d_bc81_e94f5e41161f_MD0003_00 The most common complication of twin pregnancies is preterm delivery (ie, <37 weeks gestation), which occurs due to either spontaneous preterm labor or indicated delivery for management of maternal and fetal complications. The increased risk for spontaneous preterm labor and delivery in twin gestations is likely the result of uterine crowding (eg, multiple gestations) and uterine overdistension (ie, uterine size-dates discrepancy). Uterine overdistension causes over-stretching of the myometrium, which results in an increase in prostaglandin production, number of oxytocin receptors, and contractility within the uterus. Induced preterm delivery occurs more often in twin gestations due to an increase in maternal (eg, preeclampsia) and fetal (eg, fetal growth restriction, discordant growth) complications, which require preterm delivery for disease management. Due to spontaneous preterm labor and medically indicated deliveries, more than half of all twin pregnancy deliveries occur before 37 weeks gestation. (Choice A) Fetal dysmaturity syndrome occurs in post-term (≥42 weeks gestation) pregnancies due to age-related placental changes and resultant uteroplacental insufficiency. Neonates are small for gestational age, have a thin body with loose skin, and have meconium-stained amniotic fluid. Dysmaturity syndrome does not occur in twins because they are delivered preterm or term. (Choice B) Fetal macrosomia, an estimated fetal weight ≥4,500 g, typically occurs in patients with gestational diabetes mellitus (GDM), excessive pregnancy weight gain, and some syndromes (eg, Beckwith-Wiedemann). Although women with twins are at increased risk for GDM and weight gain, fetal macrosomia does not occur as preterm delivery and uterine overcrowding limits fetal size. (Choice C) Risk factors for placenta accreta include prior uterine surgery (eg, cesarean delivery, myomectomy), particularly in patients with an associated placenta previa. Twins do not significantly increase the risk of placenta accreta. (Choice E) Uterine inversion, an obstetric emergency, occurs when the uterine fundus collapses and turns inside out during delivery of the placenta. Risk factors include fetal macrosomia, uterine anomalies, a retained placenta, and placenta accreta, not twin gestations. Educational objective: Twin pregnancies are at increased risk for preterm delivery (ie, <37 weeks gestation) due to spontaneous preterm labor and medically indicated deliveries secondary to maternal (eg, preeclampsia) and fetal (eg, fetal growth restriction) complications. References: Practice bulletin no. 169: multifetal gestations: twin, triplet, and higher-order multifetal pregnancies. (http://www.ncbi.nlm.nih.gov/pubmed/27661652) Prematurity and twinning. (http://www.ncbi.nlm.nih.gov/pubmed/23016610) A comparison of the contractile properties of myometrium from singleton and twin pregnancies. (http://www.ncbi.nlm.nih.gov/pubmed/23671701)

A 29-Year-Old Woman, Gravida 2 Para 1, at 12 Weeks