Temporal Trends in the Rates of Singletons, Twins and Higher-order Multiple Births Over Five Decades Across Racial Groups in the United States.

We analysed Natality data obtained from the National Vital Statistics System from 1971 through 2018. Overall, the rates of singletons declined among all racial groups over the five decades of the study. However, the rates of twins and higher-order multiples increased over the same period although for the past two decades, the rates of higher-order multiples had substantially plummeted. The global health implication of these findings is that policy changes in the US in the form of professional practice guidelines have succeeded in reducing the birth of vulnerable populations (i.e., higher-order multiples) who are predominantly created using assisted reproductive technology.