Snapshot A 33-year-old G2P0 woman presents for her scheduled obstretric appointment in the first trimester. She reports that she has experienced severe nausea and vomiting in the past week and has had trouble keeping any food intake down. She also endorses symptoms of fatigue and breast tenderness. An ultrasound shows the finding seen in the image. Introduction Overview multiple gestations include twins, triplets, and higher-order multiples high-risk pregnancies ↑ risk of neonatal morbidity and mortality Epidemiology Incidence twins approximately 1 in 80 pregnancies triplets 1 in 300 pregnancies Demographics ↑ maternal age associated with ↑ incidence of dizygotic twinning ↑ FSH with ↑ maternal age ↑ with assisted reproductive technology ETIOLOGY Pathophysiology ovulation of multiple follicles caused by ↑ serum gonadotropin levels twins can be monozygotic or dizygotic monozygotic - twins result from the fertilization and division of a single egg monochorionic, diamniotic twins occur if the egg splits 4-8 days after fertilization monochorionic, monoamniotic twins (rare) occur if the egg splits 8-12 days after fertilization conjoined twins (extremely rare) occur if division occurs at 13 days or later dizygotic- twins result from the fertilization and development of 2 eggs dizygotic twins are almost always dichorionic, diamniotic occurs if the egg splits 0-3 days after fertilization Presentation Symptoms may be initially asymptomatic with normal signs and symptoms of pregnancy breast tenderness fatigue nausea vomiting severe vomiting (hyperemesis gravidarum) Physical exam ↑ uterine size compared to expected based on menstrual dates Imaging Ultrasound indications most reliable method to diagnose multiple gestations optimal time for diagnosis is 1st or early 2nd trimesters findings presence of 2 separate placentas dichorionic gestation "twin peak" or "lambda" sign triangular portion of the chorion is fused between 2 layers of amnion in a dichorionic, diamniotic gestation in which the placentas have fused "T" sign appearance of the amnion as it comes off the placenta at a 90 degree angle monochorionic, diamniotic gestation Treatment Medical routine prenatal care with potentially more frequent visits and modification of activity follow recommended timing of delivery uncomplicated dichorionic, diamniotic twin gestation 38 weeks uncomplicated monochorionic, diamniotic twin gestation 34-38 weeks uncomplicated monochorionic, monoamniotic twin gestation 32-34 weeks Complications Congenital malformations 2x as common in twin pregnancies and 4x as common in triplets incidence is 4% in twins compared with 2% in singletons Intrauterine growth restriction 14-25% of twin gestations 50-60% of triplet or higher order gestations Maternal gestational diabetes incidence ↑ with each additional fetus 3-6% of twin pregnancies 22-40% of triplet pregnancies Twin-to-twin transfusion syndrome 15% of monochorionic pregnancies occurs secondary to placental vascular anastomoses leads to ↑ blood flow to 1 fetus and ↓ blood flow to the other fetus