Trends in multiple birth rates in six countries since 1950

Résumé 0

Since the 1970s, numerous countries have experienced an unprecedented increase in multiple birth rates. This is problematic because, compared to singletons, morbidity and mortality risks are higher among multiple babies and their mothers. In an effort to reduce the number of multiple births, various countries have implemented regulations in medically assisted reproduction (MAR) practices in recent years. Here we explore the trends in multiple births in Canada, Chile, Italy, Spain, the United States, and Uruguay. We find substantial variations between countries in the pace of change and in the maximum twinning and triplet + birth rates achieved. The most rapid increase and the highest peaks were observed in Spain, where access to MAR is favoured by flexible legislation, whereas the slowest increase is observed in Chile and Uruguay. In all countries, the twinning rate peaked in recent years, most likely reflecting the impact of changes in MAR practices.