Obstetrics and Gynaecology · MU Sofia

20. Multiple pregnancy

Covers twin and other multiple pregnancies, starting with how often they occur and why risk depends mainly on chorionicity. Sets out dizygotic and monozygotic origins alongside a table of when the embryo splits and the resulting placental type. Explains how to tell chorionicity on ultrasound at 11–14 weeks, then lists maternal and fetal complications in a comparison table. Ends with twin-specific complications such as twin–twin transfusion syndrome, and with growth monitoring, timing and mode of delivery.

Inside: 4 sections · 3 tables · 16 flashcards · 2 min

Topic 20 of 61 in the MU Sofia syllabus for Obstetrics and Gynaecology (Dental Medicine, Year 4). The free AceMed note covers it in 4 sections, about 214 words (2 min of reading), with 16 flashcards.

In this note

  1. Introduction
  2. Types
  3. Complications
  4. Management

Introduction

Twins occur in about 1–1.5% of births, more often with assisted reproduction and older maternal age. A multiple pregnancy carries higher risks for both mother and babies, mostly related to chorionicity.

Types

Determining chorionicity

Best done on ultrasound at 11–14 weeks: the lambda (twin-peak) sign means dichorionic; the T-sign (thin membrane meeting the placenta at a right angle) means monochorionic.

Complications

Complications of monochorionic twins

  • Twin–twin transfusion syndrome (TTTS), 10–15% of MCDA: unbalanced vascular connections; the donor is small with oligohydramnios ("stuck twin"), the recipient large with polyhydramnios and heart failure. Staged by Quintero; treated with fetoscopic laser ablation of the anastomoses.
  • Twin anaemia–polycythaemia sequence, selective growth restriction, twin reversed arterial perfusion.

Management

  • Ultrasound for growth: every 4 weeks for DCDA, every 2 weeks from 16 weeks for monochorionic twins.
  • Low-dose aspirin if other preeclampsia risk factors; iron and folic acid.
  • Timing of delivery: about 37 weeks for DCDA, 36 for MCDA, 32–34 for MCMA (by caesarean section).
  • Mode: vaginal birth is reasonable if the first twin is cephalic; caesarean if the first twin is not cephalic, for monoamniotic twins and for most higher-order multiples. After the first twin, check the second twin's lie and heart; active management of the third stage.

Chorionicity, not zygosity, decides the risk: monochorionic twins share a placenta and its vascular connections.

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