Table 4.
Relative risk of confirmed venous thrombosis in current users of different types of hormonal contraception according to length of use
| Hormonal contraception | No with confirmed venous thrombosis | Adjusted relative risk (95% CI)* | ||
|---|---|---|---|---|
| <1 year | 1-4 years | >4 years | ||
| Non-use | 1209 | 1 (reference) | 1 (reference) | 1 (reference) |
| COC with levonorgestrel and 30-40 µg oestrogen | 144 | 4.25 (3.17 to 5.69) | 3.07 (2.28 to 4.13) | 2.71 (2.06 to 3.58) |
| COC with norgestimate | 135 | 4.97 (3.86 to 6.39) | 2.97 (2.19 to 4.03) | 2.67 (1.82 to 3.92) |
| Patch | 6 | 6.89 (2.22 to 21.4) | 11.9 (3.82 to 36.9) | NA |
| Vaginal ring | 39 | 8.36 (5.73 to 12.2) | 3.83 (1.91 to 7.69) | 5.37 (1.73 to 16.7) |
| Implant | 5 | 1.63 (0.41 to 6.52) | 1.43 (0.46 to 4.45) | NA |
| Levonorgestrel IUS | 33 | 0.59 (0.34 to 1.05) | 0.61 (0.39 to 0.94) | NA |
COC=combined oral contraceptive; patch=transdermal contraceptive patch (EVRA; Johnson & Johnson, NJ, USA); implant=subcutaneous implant (Implanon; MSD, NJ, USA); vaginal ring=combined hormonal vaginal ring (NuvaRing; MSD; NJ, USA); levonorgestrel IUS=levonorgestrel intrauterine system (Mirena; Bayer Pharma, Berlin, Germany); NA=not available.
*Adjusted for age, calendar year, and education.