Multiple Gestation

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.

⭐ 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 (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.