Cox proportional HR with 95% CI for the association between childbirth, hospitalization and disability pension (DP) during year 2–5 after T0, in twins where at least one in the pair had their first delivery 1994–2009, and none before 1994.

T0 is defined as year for first childbirth for women who gave birth, and year of twin sister's first childbirth for those who did not give birth.1Twin pairs with one having DP during the follow-up and the other not (n = 53 pairs).2Twin pairs (both giving birth) with one having DP during the follow-up and the other not (n = 23 pairs).3Adjusted for birth year.4Model a, with additional adjustments for delivery year and educational level.5Model b, with additional adjustments for earlier hospitalization.6Diagnoses related to pregnancy, childbirth and the puerperium excluded (ICD-10: O80-84).