Birth spacing and the health of mothers and fathers: an analysis of physical and mental health using individual- and sibling-fixed effects

There is a large literature examining the relationship between birth spacing and subsequent health outcomes for parents, and particularly for mothers. However, research on this topic draws almost exclusively on observational research designs, and almost all studies have been limited to adjusting for observable factors that may confound the relationship between birth spacing and health outcomes. In this study we use Norwegian register data to examine the relationship between birth spacing and the number of general practitioner consultations for physical and mental health concerns for both mothers and fathers in both the period immediately after childbirth (1–5 and 6–11 months after the birth), as well as the long-term (10-11 years after the birth). To examine short-term health outcomes, we use individual-level fixed effects – examining only different births to the same parent – to hold constant factors that may influence the birth spacing behavior of mothers and fathers as well as their health. We apply sibling fixed effects in our analysis of long-term outcomes, holding constant the family background of the mothers and fathers that we study. The results from our analyses that do not apply individual or sibling fixed effects yield results consistent with much of the previous literature, where both shorter and longer birth intervals are associated with worse health outcomes than birth intervals approximately 2-3 years long. Estimates from individual fixed effects models suggest that particularly short intervals negatively affects maternal mental health in the short-term, with more ambiguous evidence that particularly short- or long-intervals may influence parental health outcomes in the short- and long-term, though some of these patterns may be consistent with selection processes.