Updated: 3/27/2020

Multiple Gestations

Review Topic
  • 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.
  • 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
  • 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
  • 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
  • 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
  • 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
  • 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

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