Monoamniotic twins: what should be the optimal antenatal management?

Abstract

Monoamniotic twinning is a rare event with an incidence of 1% of all monozygotic twins and associated with a high fetal morbidity and mortality. Confident early diagnosis is possible, but optimal management is not yet established. We present the experience of a single centre in managing seven cases of this uncommon clinical condition. A retrospective case note review of all monoamniotic twins diagnosed in a tertiary referral centre during 1994–2000 was underaken. Seven pairs of monoamniotic twins were identified for analysis. All were managed in accord with a unit protocol that involved early diagnosis, serial ultrasound examination and elective early delivery. In four cases, the detection of monoamnionicity was made during a first trimester nuchal scan. Discordance for structural abnormality was found in three cases where the co-twin was normal. Cord entanglement was detected antenatally in four cases. Two pairs of twins died before 20 weeks. One of these had early-onset twin–twin transfusion syndrome. In five cases, the pregnancy continued beyond 20 weeks. A live birth rate of 90% and intact survival of 70% were achieved in this group.