Multiple Gestation

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Multiple Gestation - Double Trouble ID

  • Types:
    • Dizygotic (DZ): Fertilization of 2 ova; always dichorionic-diamniotic (DCDA).
    • Monozygotic (MZ): Fertilization of 1 ovum, then splits. Chorionicity depends on timing of split:
      • 0-3 days: DCDA (30%)
      • 4-8 days: Monochorionic-diamniotic (MCDA) (70%)
      • 9-12 days: Monochorionic-monoamniotic (MCMA) (1%)
      • 13 days: Conjoined twins (<1%)

  • Epidemiology: ↑ with Assisted Reproductive Technology (ART), ↑ maternal age, family history.
  • Identification (Ultrasound):
    • Number of gestational sacs.
    • Chorionicity:
      • T-sign: MCDA (thin membrane)
      • Lambda (λ) sign / Twin peak sign: DCDA (thick membrane)
    • Number of fetuses, fetal heart activity.

Ultrasound: T Sign vs Lambda Sign in Twin Pregnancy

⭐ Chorionicity (determined by ultrasound via T-sign/Lambda sign) is the single most important prognostic factor in twin pregnancies.

📌 Mnemonic (Zygosity & Chorionicity): Dizygotic = Different eggs = Dichorionic. Monozygotic = Maybe one or two chorions (depends on split time).

Multiple Gestation - Mom's Twin Trials

  • Physiological Changes (Exaggerated):
    • ↑ Cardiac output (by 20% more than singleton)
    • ↑ Plasma volume (by 500-1000 mL more)
    • ↑ Tidal volume, minute ventilation
    • ↑ GFR
    • Supine hypotension syndrome more common
  • Maternal Complications:
    • Anemia (iron & folate deficiency)
    • Hyperemesis gravidarum
    • Gestational diabetes mellitus (GDM)
    • Hypertensive disorders (preeclampsia, eclampsia)
    • Thromboembolism
    • Antepartum hemorrhage (placenta previa, abruption)
    • Preterm labor & delivery (PPROM)
    • Cesarean delivery
    • Postpartum hemorrhage (uterine atony)
    • Peripartum cardiomyopathy

⭐ The risk of preeclampsia is approximately 3-4 times higher in twin pregnancies, and it often presents earlier and more severely.

  • Management: Increased surveillance, nutritional support, early recognition & management of complications. 📌 MOM'S PAL (Maternal Obstetric Monitoring; Preeclampsia, Anemia, Labor (preterm))

Multiple Gestation - Baby Bundle Bumps

  • Types: Dizygotic (2 ova), Monozygotic (1 ovum). Chorionicity (placentation) is key risk determinant.
    • DCDA: Separate placentas, lowest risk.
    • MCDA: Shared placenta, intermediate risk.
    • MCMA: Shared placenta & sac, highest risk.
  • Maternal Risks: ↑ Preeclampsia, GDM, Anemia, PPH, operative delivery.
  • Fetal Risks: ↑ Preterm birth (<37 wks), IUGR, congenital anomalies, IUFD, cerebral palsy.
  • Monochorionic (MC) Twin Complications:
    • TTTS: Unbalanced blood flow via placental anastomoses.
    • TAPS: Significant inter-twin hemoglobin difference.
    • TRAP sequence: Acardiac twin perfused by pump twin.
    • sIUGR: Due to unequal placental sharing. Twin-to-Twin Transfusion Syndrome Diagram

⭐ Twin-to-Twin Transfusion Syndrome (TTTS) affects ~10-15% of monochorionic-diamniotic (MCDA) twin pregnancies and requires specialized intervention, often laser ablation of placental anastomoses.

Multiple Gestation - Delivery Duet

  • Antenatal Surveillance:
    • Growth scans: DCDA q4wks (from 20wks); MCDA/MCMA q2wks (from 16wks).
    • MCMA: Inpatient monitoring often 28-32 wks.
  • Timing & Mode:
> ⭐ Optimal timing for delivery: uncomplicated DCDA twins **37+0 to 37+6** weeks, MCDA twins **34+0 to 36+6** weeks, and MCMA twins **32+0 to 34+0** weeks (often by elective C-section to prevent cord accidents).
  • Delivery Mode:
    • Vaginal: Twin 1 cephalic, no contraindications.
    • CS: Twin 1 non-cephalic, fetal distress, MCMA (often), other complications (e.g., IUGR).

High‑Yield Points - ⚡ Biggest Takeaways

  • Chorionicity is the single most critical factor determining outcomes in multiple gestations.
  • Monochorionic (MC) twins face high risks: TTTS, TAPS, sIUGR.
  • Dichorionic (DC) twins generally have more favorable outcomes.
  • Ultrasound: Lambda (λ) sign indicates dichorionicity; T-sign indicates monochorionicity.
  • All multiple pregnancies carry ↑ risk of preterm labor, preeclampsia, GDM, and PPH.
  • Vanishing twin syndrome is a frequent finding in early pregnancy.
  • Optimal delivery mode depends on GA, presentation of Twin 1, and chorionicity.

Practice Questions: Multiple Gestation

Test your understanding with these related questions

Which of the following is NOT a characteristic of the recipient twin in a monochorionic twin gestation affected by twin-twin transfusion syndrome?

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Flashcards: Multiple Gestation

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In Quintero stage _____, there will be frank ascites or hydrops in either twin

TAP TO REVEAL ANSWER

In Quintero stage _____, there will be frank ascites or hydrops in either twin

IV

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