Table 2.
Cox proportional HR with 95% CI for the association between childbirth, hospitalisation before T0, and subsequent hospitalisation (ie, during year 3–5 after T0) in twins where at least one in the pair had her first childbirth during 1994–2009 and none before 1994, both including and excluding hospitalisation related to pregnancy, childbirth and the puerperium
| Status childbirth and hospitalisation | All diagnoses |
Diagnoses related to pregnancy, childbirth and the puerperium excluded* | ||||
|---|---|---|---|---|---|---|
| Model a† | Model b‡ | Discordant twin pairs§,‡ | Model a† | Model b‡ | Discordant twin pairs¶,‡ | |
| All women (n=5118) | ||||||
| No childbirth, no hospitalisation before T0** | 1 (REF) | 1 (REF) | 1 (REF) | 1 (REF) | 1 (REF) | 1 (REF) |
| No childbirth, hospitalisation before T0** | 2.5 (1.7 to 3.6) | 2.3 (1.6 to 3.3) | 2.4 (1.3 to 4.5) | 2.7 (1.8 to 3.9) | 2.3 (1.6 to 3.4) | 1.2 (0.8 to 1.9) |
| Childbirth, no hospitalisation before T0** | 6.1(5.0 to 7.5) | 5.5 (4.5 to 6.8) | 8.3 (5.8 to 11.8) | 1.1 (0.8 to 1.3) | 0.9 (0.7 to 1.2) | 0.9 (0.7 to 1.1) |
| Childbirth, hospitalisation before T0** | 6.5 (5.2 to 8.1) | 5.6 (4.4 to 7.1) | 7.9 (5.4 to 11.5) | 1.9 (1.4 to 2.5) | 1.4 (1.1 to 1.9) | 0.9 (0.7 to 1.2) |
| Model a† | Model b‡ | Discordant twin pairs††,‡ | Model a† | Model b‡ | Discordant twin pairs‡‡,‡ | |
| Women who had at least one childbirth (n=2792) | ||||||
| No hospitalisation before T0** | 1 (REF) | 1 (REF) | 1 (REF) | 1 (REF) | 1 (REF) | 1 (REF) |
| Hospitalisation before T0** | 1.0 (0.9 to 1.2) | 1.0 (0.9 to 1.1) | 1.0 (0.8 to 1.2) | 1.7 (1.3 to 2.3) | 1.5 (1.2 to 2.0) | 1.0 (0.8 to 1.3) |
Two models for adjustments as well as for discordant twin pairs.
*Diagnoses O00-O99.
†Adjusted for birth year.
‡Model a, and additional adjustments for delivery year and educational level.
§Twin pairs where one had a hospitalisation during the follow-up and the other did not (n=1016 pairs).
¶Twin pairs where one had a hospitalisation during the follow-up and the other did not (n=456 pairs).
**During the period 1–5 years prior to T0.
††Twin pairs (both giving birth) where one had a hospitalisation during the follow-up and the other did not (n=508 pairs).
‡‡Twin pairs (both giving birth) where one had a hospitalisation during the follow-up and the other did not (n=271 pairs).