Since the mid-1990s, as a result of assisted reproductive technology, the incidence of twin pregnancy has doubled and the number of triplets has increased ten-fold. Compared with singleton pregnancies, the perinatal morbidity and mortality of twins is increased five- to ten-fold and to a much greater degree for triplets and higher-order multiple births. Overall, multiple pregnancies account for about 3% of all births but contribute approximately 25% of early preterm births (less than 32 weeks of gestation), low-birthweight infants (under 2500 g), and very low-birthweight infants (under 1500 g). Compared with singletons, the incidence of cerebral palsy is increased eight-fold in twins and about 40-fold with triplets. The main determinants of this increase in morbidity and mortality are prematurity, growth restriction, anomalies and twin-to-twin transfusion. Asphyxia and trauma during delivery make a smaller contribution to morbidity and mortality but can be all the more tragic when the safe conclusion of a high-risk pregnancy is at hand. It is therefore understandable that in many developed countries the caesarean section rate for twins has roughly doubled, from 25% to 50%, since the mid-1990s, although there is no proof that abdominal delivery is safer for the infants. An international randomised trial is under way to determine the safest mode of delivery.

However, it is clear that, irrespective of the mode of delivery, twins should be delivered in hospitals with adequate anaesthetic, obstetric and neonatal personnel and facilities.