Short Interpregnancy Intervals in the United States

OBJECTIVE: To investigate the prevalence and correlates of short interpregnancy intervals in the United States. METHODS: We analyzed pregnancy data from a nationally representative sample of 12,279 women from the 2006-2010 National Survey of Family Growth. We limited our sample to second and higher-order births within 5 years of the interview. Interpregnancy intervals were calculated as the interval between the delivery date of the preceding live birth and the conception date of the index pregnancy, with short interpregnancy intervals defined as intervals less than 18 months. We used simple and multivariate logistic regression analyses to examine associations between short interpregnancy intervals and maternal demographic and childbearing characteristics, including pregnancy intention. RESULTS: Among the 2,253 pregnancies in our sample, one third (35%) were conceived within 18 months of a previous birth. After adjusting for sociodemographic and childbearing characteristics, women were significantly more likely to have a short interpregnancy interval if they were aged 15-19 years or married at the time of conception of the index pregnancy, initiated childbearing after age 30 years, or reported the pregnancy as unintended. Short interpregnancy intervals were more likely to be intended among more advantaged women (married, non-Hispanic white, college-educated, or non-Medicaid delivery). We estimate that preventing unintended pregnancies would reduce the proportion of short interpregnancy intervals from 35% to 23%. CONCLUSION: Providing counseling about the potential negative consequences of short interpregnancy intervals and improving women's contraceptive use to reduce rates of unintended pregnancy likely would reduce the proportion of short interpregnancy interval pregnancies in the United States.