Trends in multiple births, 1938-1995.

Information about multiple births has been collected at birth registration in England and Wales since 1938. This article describes the changes and trends in the prevalence of multiple births since that date. Particular attention is given to the increasing incidence of multiple births since the mid-1970s. Geographical variations in multiple births and differences by social class (based on occupation) are analysed. Age at motherhood is found to be a significant factor influencing the changes since 1938.