title: Associations between childbirth, hospitalization and disability pension: a cohort study of female twins.
abstract: 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.
authors.affiliation: Department of Clinical Neuroscience, Division of Insurance Medicine, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Emma
authors.initials: E
authors.lastname: Björkenstam
authors.affiliation: Department of Clinical Neuroscience, Division of Insurance Medicine, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Jurgita
authors.initials: J
authors.lastname: Narusyte
authors.affiliation: Department of Clinical Neuroscience, Division of Insurance Medicine, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Kristina
authors.initials: K
authors.lastname: Alexanderson
authors.affiliation: Finnish Institute of Occupational Health, Helsinki, Finland.
authors.forename: Annina
authors.initials: A
authors.lastname: Ropponen
authors.affiliation: Department of Clinical Neuroscience, Division of Insurance Medicine, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Linnea
authors.initials: L
authors.lastname: Kjeldgård
authors.affiliation: Department of Clinical Neuroscience, Division of Insurance Medicine, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Pia
authors.initials: P
authors.lastname: Svedberg
mesh_terms: D000293:Adolescent; D000328:Adult; D015331:Cohort Studies; D006233:Persons with Disabilities / Q000706:statistics & numerical data*; D005190:Family; D005260:Female; D006760:Hospitalization / Q000706:statistics & numerical data*; D006801:Humans; D008875:Middle Aged; D036801:Parturition; D010415:Pensions / Q000706:statistics & numerical data*; D011247:Pregnancy; D012306:Risk; D013548:Sweden / Q000453:epidemiology; D055815:Young Adult