Contribution of Multiple Pregnancies to Perinatal Mortality and Morbidity

Multiple pregnancies have increased from 9 per 1000 pregnancies in the 1970s to 14 per 1000 pregnancies. Multiple births account for 10% of perinatal deaths (8% of fetal deaths and 14% of neonatal deaths). Compared to singletons births, the perinatal mortality rate is four times higher in twins, and nine times higher in multiple births of a higher order. The cerebral palsy rate among survivors is five times higher in twins and nineteen times higher is multiple births of a higher order. Monochorionic monozygotic twins are at the highest risk, due firstly to the cell division process leading to chromosomal or other anomalous lethal aberration in one fetus, and secondly to twinto-twin transfusion syndrome (TTTS) and its adverse consequences on the surviving fetus if there is fetal death of its co-twin. The incidence of TTTS is 15-30% in monochorionic monozygotic twins. Data are emerging on the obstetric risks, survival and neurological outcome associated with interventions for treating TTTS (serial amnioreduction, fetoscopic laser ablation of placental vascular anastomoses, amniotic septostomy, and selective feticide), and several randomised controlled trials are in progress.