Intentionally or Ambivalently Risking a Short Interpregnancy Interval: Reproductive-Readiness Factors in Women’s Postpartum Non-Use of Contraception


A focus of research on short interpregnancy intervals (IPI) has been on young disadvantaged women whose births are likely to be unintended. Later initiation of family formation in the United States and other high-income countries points to the need to also consider a woman’s attributes indicative of readiness for purposefully accelerated family formation achieved through short IPIs. We test for whether factors indicating “reproductive readiness”—including being married, being older, and having just had a first birth or a birth later than desired—predict a woman’s non-use of contraception in the postpartum months. We also test for whether this contraceptive non-use results explicitly from wanting to become pregnant again. The data come from the 2012–2015 Pregnancy Risk Assessment Monitoring System, representing women who recently gave birth in any of 35 U.S. states and New York City (N = 120,111). We find that these reproductive-readiness factors are highly predictive of women’s postpartum non-use of contraception because of a stated desire to become pregnant and are moderately predictive of contraceptive non-use without an explicit pregnancy intention. We conclude that planning for, or ambivalently risking, a short IPI is a frequent family-formation strategy for women whose family formation has been delayed. This is likely to become increasingly common as family formation in the United States is initiated later in the reproductive life course.

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Fig. 1


  1. 1.

    Our aims here were to err on the side of inclusivity of women who may be ambivalently risking a short IPI and to avoid selectively excluding women who did not report using another contraceptive method when they marked abstinence as a contraceptive method. As a sensitivity check, we reran our regressions excluding the 3,301 women in our analytical sample (a weighted 2.6% of the total) who reported that they were using abstinence as a contraceptive method and who marked no other method. The results were very similar to those from our reported models.


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The data and documentation are provided by the PRAMS Working Group and the Centers for Disease Control and Prevention. We thank Michel Boudreaux and Julia Steinberg, and participants at the annual meeting of the 2018 Population Association of America and the Johns Hopkins University Population, Family and Reproductive Health seminar series, for comments on earlier versions. This work was supported by the Eunice Kennedy Shriver National Institute of Child Health and Human Development, population research infrastructure grant P2C-HD041041, and a research grant from a private philanthropic foundation.

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Correspondence to Michael S. Rendall.

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Rendall, M.S., Harrison, E.Y. & Caudillo, M.L. Intentionally or Ambivalently Risking a Short Interpregnancy Interval: Reproductive-Readiness Factors in Women’s Postpartum Non-Use of Contraception. Demography 57, 821–841 (2020).

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  • Fertility timing
  • Birth spacing
  • Contraception