• cord entanglement;
  • fetal monitoring;
  • monoamniotic twins;
  • perinatal outcome

Key content

  • Monoamniotic twins are believed to account for 1–5% of all monozygotic conceptions, with an estimated annual incidence of 30–150 pregnancies in the UK.
  • High perinatal loss rates in monoamniotic twins have been attributed mainly to umbilical cord entanglement, inter-twin transfusion syndrome, discordant fetal abnormality or fetal growth restriction.
  • Management of monoamniotic twin pregnancy is aimed at preventing antenatal fetal death and optimising timing of delivery.
  • Despite the paucity of robust data on the incidence and causes of perinatal loss, elective delivery at 32–34 weeks of gestation has been proposed.
  • Most obstetric units use caesarean birth as the preferred mode of delivery for monoamniotic twins to prevent intrapartum cord complications.

Learning objectives

  • To understand the aetiology, incidence and diagnosis of monoamnionicity.
  • To be able to identify the type and prevalence of complications in monoamniotic twins.
  • To be aware of the current evidence on the antenatal management and optimal timing of delivery of monoamniotic twin pregnancy.

Ethical issues

  • Can we justify elective preterm delivery and its subsequent complications without a robust evidence base demonstrating a reduction in perinatal morbidity and mortality?