EXAMINING THE ASSOCIATION BETWEEN INTERPREGNANCY INTERVAL AND MATERNAL HEALTH IN THE POSTPARTUM PERIOD

Abstract

Interpregnancy interval (IPI) is defined as the period of time between a previous birth and a subsequent conception, usually measured in months. While recommendations issued by the World Health Organization and the American College of Obstetricians and Gynecologists provide guidance for ideal birth spacing, many births occur after non-optimal IPIs – either too short (<18 months) or too long (60+ months). These recommendations were motivated by the body of research on a host of adverse infant and maternal health outcomes associated with non-optimal IPIs. To date, the literature has focused heavily on the association between IPI and adverse infant health outcomes, with limited attention in comparison being given to IPI and maternal health. Within the research on IPI and maternal health, there is a narrow focus on physical health outcomes related to pregnancy/delivery complications, with few studies looking at health outcomes in the postpartum and beyond. In order to fill this gap, this research investigated the association between IPI and several postpartum maternal health outcomes/indicators, including 1) postpartum depression (PPD), 2) attendance at a postpartum checkup, and 3) postpartum contraceptive use (any and type). One of the perennial difficulties in studying IPI is parsing out whether IPI has an independent association with a health outcome or behavior or is exerting its effects through pregnancy intention, therefore, for each aim, pregnancy intention was tested as a moderator. For each aim, unique cut-offs for IPI were determined after examination of the association between more detailed IPI categories and the outcome of interest. Categories were collapsed into broader IPI classifications when the associations were similar in order to maximize precision of the estimates and in order to allow us to characterize the most clinically relevant exposure for specific health outcomes. In fully adjusted models, individuals who had IPIs less than 18 months were significantly more likely to experience elevated PPD symptoms (aOR: 1.19, 95% CI: 1.02 – 1.39, p=0.024) when compared to individuals with long IPIs, and individuals who had IPIs less than 12 months were significantly less likely to attend their postpartum checkup (aOR: 0.78, 95% CI: 0.66 – 0.93, p=0.006) when compared to those with long IPIs. Pregnancy intention was not found to significantly moderate either of these associations. For the third aim, pregnancy intention was found to moderate the association between IPI and any use of postpartum contraception. Stratified analyses show that it is among unintended pregnancies that there is an association between short IPI and increased use of any contraception in the postpartum. Among unintended pregnancies, those with IPIs less than 6 months (aOR: 2.31, 95% CI: 1.37 – 3.90, p=0.002) and those with IPIs of 6-11 months (aOR: 2.15, 95% CI: 1.48 – 3.10, p=0.001) were more likely to be using any contraception in the postpartum than those with long IPIs, and the magnitude of this association exceeded that of other IPI intervals and pregnancy intention categories. Among those who were using contraception in the postpartum, individuals with IPIs less than 6 months were more likely to be using highly-effective methods (aOR: 1.59, 95% CI: 1.22 – 2.10, p=0.001) than least-effective methods of contraception. Pregnancy intention did not significantly moderate the association between IPI and type of contraception. Future research should continue to explore the association between IPI and a broader range of maternal health outcomes and work to identify the mechanisms through which IPI may be impacting these outcomes. Recent changes in reproductive policies in the U.S. may also soon change the proportion of individuals who experience short IPIs, therefore making it even more important to understand how this shift may impact a broad range of maternal health behaviors and outcomes. This research highlights how an increase in births occurring after a short IPI would likely increase rates of PPD and increase demand for certain family planning services.