Table 1.
Cohort characteristics for twins (women with a twin sister) born in Sweden during 1959–1990 (excluding those who gave birth before age 16 and those who died before age 16), where at least one in the pair had their first childbirth during 1994–2009 and none before 1994
| Variables | Both gave birth | Twin pairs where only one in the pair gave birth |
Total | |
|---|---|---|---|---|
| Twin 1 (gave birth) | Twin 2 (did not give birth) | |||
| N | 2792 | 1163 | 1163 | 5118 |
| Number of deliveries | ||||
| One delivery | 711 (25%) | 501 (43%) | ||
| Two or more deliveries | 2081 (75%) | 662 (57%) | ||
| Age at T0 (years) | ||||
| 16–19 | 47 (2%) | 33 (2%) | ||
| 20–24 | 511 (18%) | 239 (21%) | ||
| 25–29 | 1150 (41%) | 444 (38%) | ||
| 30–34 | 847 (30%) | 323 (28%) | ||
| 35–39 | 207 (7%) | 109 (9%) | ||
| >40 | 30 (1%) | 15 (1%) | ||
| Zygosity | ||||
| Monozygotic | 1726 (62%) | 608 (52%) | 608 (52%) | 2942 (57%) |
| Dizygotic | 1066 (38%) | 555 (48%) | 555 (48%) | 2176 (43%) |
| Highest attained education* (years) | ||||
| ≤9 | 179 (6%) | 74 (6%) | 55 (5%) | 308 (6%) |
| 10–12 | 1434 (51%) | 608 (52%) | 621 (53%) | 2663 (52%) |
| ≥13 | 1173 (42%) | 474 (41%) | 422 (36%) | 2069 (40%) |
| Information on education missing | 6 (0%) | 7 (1%) | 65 (6%) | 78 (2%) |
| Hospitalisation† | ||||
| At least one hospitalisation during the period 6 years prior through 6 years after T0 | 2161 (77%) | 703 (60%) | 325 (28%) | 3189 (62%) |
| At least one hospitalisation during the period 6 years prior through 6 years after T0 (excluding hospitalisations with a diagnosis for pregnancy, childbirth and the puerperium) | 865 (31%) | 315 (27%) | 314 (27%) | 1494 (29%) |
| At least one hospitalisation during the period 6 years prior through 6 years after T0 (excluding hospitalisations with a diagnosis for pregnancy, and childbirth) | 1183 (42%) | 407 (35%) | 325 (28%) | 1915 (37%) |
| At least one hospitalisation during the period 6 years prior to T0 | 679 (24%) | 251 (22%) | 217 (19%) | 1147 (22%) |
| At least one hospitalisation during the period 6 years after T0 | 1965 (70%) | 585 (50%) | 168 (14%) | 2718 (53%) |
| At least one hospitalisation both before and after T0 | 483 (17%) | 133 (11%) | 60 (5%) | 676 (13%) |
| SA‡ | ||||
| At least one SA during the period 6 years prior through 6 years after T0 | 1526 (55%) | 530 (46%) | 365 (31%) | 2420 (47%) |
| At least one SA during the period 6 years prior to T0 | 690 (25%) | 274 (24%) | 224 (19%) | 1188 (23%) |
| At least one SA during the period 6 years after T0 | 1245 (45%) | 382 (33%) | 221 (19%) | 1848 (36%) |
T0 is defined as the year for first childbirth for women who gave birth, and as the year of the twin sister's childbirth for those who did not give birth.
*At the time of T0.
†Excluding hospitalisations occurring during T0.
‡Excluding SA occurring during T0.
SA, sickness absence.