HIV Insight: Cohort Trends in Premarital First Births: What Role for the Retreat from Marriage?

We examine cohort trends in premarital first births for U.S. women born between 1920 and 1964. The rise in premarital first births is often argued to be a consequence of the retreat from marriage, with later ages at first marriage resulting in more years of exposure to the risk of a premarital first birth. However, cohort trends in premarital first births may also reflect trends in premarital sexual activity, premarital conceptions, and how premarital conceptions are resolved.

We decompose observed cohort trends in premarital first births into components reflecting cohort trends in

the age-specific risk of a premarital conception taken to term;
the age-specific risk of first marriages not preceded by such a conception, which will influence women’s years of exposure to the risk of a premarital conception; and
whether a premarital conception is resolved by entering a first marriage before the resulting first birth (a “shotgun marriage”).

For women born between 1920–1924 and 1945–1949, increases in premarital first births were primarily attributable to increases in premarital conceptions. For women born between 1945–1949 and 1960–1964, increases in premarital first births were primarily attributable to declines in responding to premarital conceptions by marrying before the birth.

Trends in premarital first births were affected only modestly by the retreat from marriages not preceded by conceptions—a finding that holds for both whites and blacks.

These results cast doubt on hypotheses concerning “marriageable” men and instead suggest that increases in premarital first births resulted initially from increases in premarital sex and then later from decreases in responding to a conception by marrying before a first birth.

Below: Conceptual model of first births occurring within and outside of a first marriage. Women begin in an origin state (0) in which they have never been married, have not had a birth, and are not currently pregnant. From this origin state, some women may transition to either (1) a premarital conception or (2) a first marriage not preceded by a conception that was subsequently taken to term. The reverse arrow from (1) to (0) denotes the possibility that some women who have a premarital conception may return to the origin state because of an induced abortion, a miscarriage, or fetal death. The model also assumes that those with a premarital conception taken to term will resolve the conception with either (3) a premarital first birth or (4) a first birth following a postconception first marriage. Finally, a marital first birth may occur to women who conceived during a first marriage (5)

Below: Observed, predicted, and counterfactual trends in the percentage of women by age 25 experiencing a premarital conception taken to term and resulting in a first birth for white women (panel a) and black women (panel b), by birth cohort. Predicted trends are obtained from model estimates for the competing risks of a premarital conception taken to term versus a first marriage not preceded by conception, as reported in Table 3. The line labeled “Counterfactual: no trend in preconception first marriage, estimated trend in premarital conceptions” refers to a counterfactual trend obtained from estimated cohort trends in premarital conceptions taken to term but imposing a counterfactual of no trend in preconception first marriage (i.e., first marriages not preceded by conceptions). The line labeled “Counterfactual: no trend in premarital conceptions, estimated trend in preconception first marriage” refers to a counterfactual trend obtained from estimated cohort trends in preconception first marriage but imposing a counterfactual of no trend in premarital conceptions taken to term. See the text, Table 3, and Online Resource 2 for additional details

Below: Observed and predicted percentages of white women and black women experiencing a premarital conception by age 25 who marry before the birth, by birth cohort. Predicted trends are obtained from logistic regression model estimates conditional on a premarital conception taken to term. See the text for additional details

Below: Observed and predicted percentages of white women and black women experiencing a premarital first birth by age 25, by birth cohort. Predicted trends are obtained by combining model estimates from the competing-risk and logistic regression models, as reported in Table 4. See the text and Online Resources 1–3 for additional details