Early childbearing and children's achievement and behavior over time.

CONTEXT: Compared with children of older women, children of women who had their first birth during their teens have long been believed to be at higher risk for a host of poor health, social and economic outcomes. Recent studies have failed to confirm this belief, but none have taken into account whether children's outcomes or the effects of early childbearing on those outcomes have changed over time.
METHODS: Data from the National Longitudinal Survey of the Labor Market Experience of Youth and the Panel Study of Income Dynamics are used to separate the influence of changes from the 1960s through the 1990s in children's experiences from the effect of mother's age at first birth.
RESULTS: Multivariate analyses controlling for social and demographic characteristics show that among children born to women from a particular birth cohort, those whose mothers first gave birth in their teens have significantly lower scores on a set of four achievement tests and significantly higher scores on a behavior-problem index than do children whose mothers delayed childbearing. However, when changes over time in children's outcomes and in the effect of early childbearing on those outcomes are taken into account, children born to women who began childbearing early score significantly worse than those whose mothers delayed their first birth on the behavior-problem index, but on only one achievement test.
CONCLUSIONS: Comparisons by age at first birth among women born in the same period may misestimate the effects of early motherhood. Whether early childbearing's effects on children are overestimated or underestimated depends on whether test scores are rising or falling. Policymakers should be cautious in making decisions based on studies that do not take time trends into account.