Differences between mistimed and unwanted pregnancies among women who have live births.

Context: Mistimed and unwanted pregnancies that result in live births are commonly considered together as unintended pregnancies, but they may have different precursors and outcomes.

Methods: Data from 15 states participating in the 1998 Pregnancy Risk Assessment Monitoring System were used to calculate the prevalence of intended, mistimed and unwanted conceptions, by selected variables. Associations between unintendedness and women's behaviors and experiences before, during and after the pregnancy were assessed through unadjusted relative risks.

Results: The distribution of intended, mistimed and unwanted pregnancies differed on nearly every variable examined; risky behaviors and adverse experiences were more common among women with mistimed than intended pregnancies and were most common among those whose pregnancies were unwanted. The likelihood of having an unwanted rather than mistimed pregnancy was elevated for women 35 or older (relative risk, 2.3) and was reduced for those younger than 25 (0.8); the pattern was reversed for the likelihood of mistimed rather than intended pregnancy (0.5 vs. 1.7-2.7). Parous women had an increased risk of an unwanted pregnancy (2.1-4.0) but a decreased risk of a mistimed one (0.9). Women who smoked in the third trimester, received delayed or no prenatal care, did not breast-feed, were physically abused during pregnancy, said their partner had not wanted a pregnancy or had a low-birth-weight infant had an increased risk of unintended pregnancy; the size of the increase depended on whether the pregnancy was unwanted or mistimed.

Conclusion: Clarifying the difference in risk between mistimed and unwanted pregnancies may help guide decisions regarding services to women and infants.