Recent secular trends in dizygotic twinning rates in Europe

Abstract

SummaryIn all European countries for which data exist, there was a maternal-age-specific decline in dizygotic twinning rates during the 1960s. For most of these countries, this decline continued through the 1970s, but in a few it apparently ceased. The causes of the declines and of their abatement are unknown. However, there were declines in sperm quality during the 1960s and 1970s in some parts of the world, including parts of Europe, and it is speculated here that this decline in sperm quality may be related to the decline in dizygotic twinning.