Cohabitation, post-conception unions, and the rise in nonmarital fertility.

The majority of U.S. nonmarital births today are to cohabiting couples. This study focuses on transitions to cohabitation or marriage among pregnant unmarried women during the period between conception and birth. Results using the newly-released 2006-2010 National Survey of Family Growth show that nonmarital pregnancy is a significant precursor to cohabitation before childbirth (18%), exceeding transitions to marriage (5%) by factor of over three. For pregnant women, the boundaries between singlehood, cohabitation, and marriage are highly fluid. The results also reveal substantial variation in post-conception cohabiting and marital unions; e.g., disproportionately low percentages of black single and cohabiting women transitioned into marriage, even when conventional social and economic risk factors are controlled. The multivariate analyses also point to persistent class differences in patterns of family formation, including patterns of cohabitation and marriage following conception. Poorly educated women, in particular, are much more likely to become pregnant as singles living alone or as partners in cohabiting unions. But compared with college-educated women, pregnancies are less likely to lead to either cohabitation or marriage. This paper highlights the conceptual and technical challenges involved in making unambiguous interpretations of nonmarital fertility during a period of rising nonmarital cohabitation.