Cox proportional HR with 95% CI for the association between hospitalization before and after first childbirth, and DP during year 2–5 after first childbirth, in twins who had their first delivery 1994–2009 (n = 2 756).

1Twin pairs with one twin having DP during the follow-up and the other not (n = 23 pairs).2Twin pairs with one twin having a mental DP diagnosis during the follow-up and the other not (n = 22 pairs).3Twin pairs with one twin having a musculoskeletal DP diagnosis during the follow-up and the other not (n = 10 pairs).4Adjusted for birth year.5Model a, with additional adjustments for delivery year, and educational level.6During the period 1–5 years prior to T0.7Diagnoses related to pregnancy, childbirth and the puerperium excluded (ICD-10: O80-84).