New Partners, More Kids: Multiple-Partner Fertility in the United States.

Declining rates of marriage and overall increases in union instability, combined with high levels of unintended and nonmarital fertility, create the possibility for parents to have children with more than one partner, called multiple-partner fertility, or MPF. The unique characteristics of families with MPF present data and other logistical challenges to researchers studying the phenomenon. Drawing from recent studies and updated data, I present new estimates of MPF that show that about 13 percent of men aged 40 to 44 and 19 percent of women aged 41 to 49 have children with more than one partner, with a higher prevalence among the disadvantaged. Compared to parents with two or more children by only one partner, people with MPF become parents at younger ages, largely with unintended first births, and often do so outside of marriage. This article touches on the implications of MPF for families and concludes by discussing the theoretical difficulties in studying MPF and the challenges it presents to public policy.