Recent trends in the incidence of multiple births and associated mortality.

The overall incidence of multiple births in England and Wales, which had been declining since the early 1950s, started to increase in the early 1980s in all age groups except for women under 20. This followed a rise in the incidence of triplet and higher order multiple births which had started in the late 1970s. Analyses of data for births between 1978 and 1983 showed that while stillbirth, perinatal, neonatal, and post-neonatal mortalities among multiple births fell considerably, they remained consistently higher than those for singleton births. Differences in the distribution of birth weight do not wholly explain these differences. Analyses of certified causes of stillbirth and death are difficult to interpret because a considerable proportion were attributed to 'multiple pregnancy'.