Cohort characteristics for twins (women with twin sister) born in Sweden 1959–1990 (excluding those who delivered before age 16 and those who died before age 16), 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.
1At T0
2Excluding hospitalizations occurring during T0