Birth spacing and health and socioeconomic outcomes across the life course: evidence from the Utah Population Database
Demography (2022), accepted
The relationship between the length of birth intervals and child outcomes has received increased attention in recent years, but few studies have examined offspring outcomes across the life course in North America. In this study we examine the relationship between birth intervals and a range of short- and long-term outcomes, including preterm birth, low birth weight, infant mortality, college graduation, occupational attainment, and adult mortality, using data from the Utah Population Database (UPDB). To study infant outcomes we use data on cohorts born 1947--2019, to study educational and occupational outcomes we use data on cohorts born 1950--1990, and to study adult mortality we use data on cohorts born 1900--1949, with mortality outcomes followed until 2019. We use linear regression, linear probability models, and survival analysis, and compare the results from models with and without sibling comparisons. Children born after a birth interval of 9-12 months have a higher probability of low birth weight, preterm birth, and infant mortality both with and without sibling comparisons, while longer intervals are associated with a lower probability of these outcomes. Short intervals before the birth of the next youngest sibling are also associated with LBW, preterm birth, and infant mortality both with and without sibling comparisons. This pattern raises concerns that the sibling comparison models are not fully adjusting for within-family factors predicting both spacing and perinatal outcomes. Considering long-term outcomes, not even the very shortest birth intervals are negatively associated with educational or occupational outcomes, nor long-term mortality, in sibling comparison analyses. These findings suggest that extremely short birth intervals may increase the probability of poor perinatal outcomes, but that any such disadvantages disappear over the extended life course.
Keywords: USA, adult education, adult mortality, birth spacing, birth weight, infant mortality, occupational mobility, siblings