BACKGROUND: As the literature on long-term effects of childbirth on risk of morbidity or permanent work incapacity (DP) is limited, we aimed to study associations of childbirth with hospitalization and DP, adjusting for familial factors.

METHODS: This cohort study included female twins, i.e. women with twin sister, born 1959-1990 in Sweden (n = 5 118). At least one in the twin pair had their first childbirth 1994-2009. Women were followed regarding all-cause and cause-specific (mental or musculoskeletal diagnoses) DP during year 2-5 after first delivery or equivalent. Associations between childbirth, hospitalization and DP were calculated as hazard ratios (HR) with 95% confidence intervals (CI).

RESULTS: Women who did not give birth had markedly higher number of DP days/year compared to those giving birth. Hospitalization after first childbirth was associated with a higher HR of DP. Those hospitalized at least once after their first childbirth had a three-fold DP risk (HR: 3.2; 95% CI 1.1-9.6), DP due to mental diagnoses (HR: 3.2; 1.2-8.8), and of DP due to musculoskeletal diagnoses (HR: 6.1; 1.6-22.9). Lower HRs in the discordant twin pair analyses indicated that familial factors may influence the studied associations.

CONCLUSIONS: Women who did not give birth had a much higher risk for DP than those who did. Among those who gave birth, the risk for DP was markedly higher among those with a previous hospitalization, and especially in women with repeated hospitalizations. The results indicate a health selection into giving birth as well as the importance of morbidity for DP.