Table 7.
Relative risk of venous thromboembolism in current users of different combined oral contraceptives according to study. Non-users of hormonal contraception as reference group unless specified otherwise
| Study | Sampling period | No of events* | Relative risk (95% CI) | ||
|---|---|---|---|---|---|
| COC with levonorgestrel | COC with third generation progestogens† | COC with drospirenone | |||
| Bloemenkamp1 | 1988-92 | 126 | 3.8 (1.7 to 8.4) | 8.7 (3.9 to 19.3) | NA |
| WHO4 | 1989-93 | 433 | 3.6 (2.5 to 5.1) | 7.4 (4.2 to 12.9) | NA |
| Jick2 | 1991-4 | 80 | 1 (Reference) | 1.8 (1.0 to 3.2) | NA |
| Spitzer5 | 1991-5 | 471 | 3.7 (2.2 to 6.2) | 6.7 (3.4 to 13) | NA |
| Farmer6 | 1991-5 | 85 | 3.1‡ (2.1 to 4.5) | 5.0‡ (3.7 to 6.5) | NA |
| Lewis8 | 1993-5 | 502 | 2.9 (1.9 to 4.2) | 2.3 (1.5 to 3.5) | NA |
| Todd9 | 1992-7 | 99 | 1 (Reference) | 1.4 (0.7 to 2.8) | NA |
| Bloemenkamp7 | 1994-8 | 185 | 3.7 (1.9 to 7.2) | 5.6 (NA) | NA |
| Lidegaard13 | 1994-8 | 987 | 2.9 (2.2 to 3.8) | 4.0 (3.2 to 4.9) | NA |
| Dinger14 | 2000-4 | 118 | 1 (Reference) | 1.3 (NS) | 1.0 (0.6 to 1.8) |
| Vlieg17 | 1999-2004 | 1524 | 3.6 (2.9 to 4.6) | 7.3 (5.3 to 10.0) | 6.3 (2.9 to 13.7) |
| Lidegaard18 | 1995-2005 | 4213 | 2.0 (1.8 to 2.3) | 3.6 (3.3 to 3.8) | 4.0 (3.3 to 4.9) |
| Dinger19 | 2002-8 | 680 | 1 (Reference) | NA | 1.0 (0.6 to 1.8) |
| Parkin20 | 2002-9 | 61 | 1 (Reference) | NA | 2.7 (1.5 to 4.7) |
| Jick21 | 2002-8 | 186 | 1 (Reference) | NA | 2.8 (2.1 to 3.8) |
| Present study: | |||||
| All reported events* | 2001-9 | 4246 | 2.2 (1.7 to 2.8) | 4.2 (3.6 to 4.9) | 4.5 (3.9 to 5.1) |
| Confirmed events only* | 2001-9 | 2707 | 2.9 (2.2 to 3.8) | 6.8 (5.7 to 8.1) | 6.3 (5.4 to 7.5) |
COC=combined oral contraceptives; NA=not available; NS=non-significant.
*Events are venous thromboembolisms.
†Desogestrel or gestodene.
‡Absolute risk per 10 000 women years.