Table 2.
Oral contraceptive characteristics among ever OC users in the Nurses’ Health Study II by total duration of OC use in 1989 (n=91,935)a
| ≤6 months OC use (n=9,770) | >6 months to 1 year OC use (n=9,065) | >1-<5 years OC use (n=36,026) | 5-<10 years OC use (n=27,800) | 10-<15 years OC use (n=7,857) | ≥15 years OC use (n=1,417) | |
|---|---|---|---|---|---|---|
| Mean (Standard deviation) | ||||||
| Estrogenb,c | ||||||
| Cumulative dose | 6,330 (2,969) | 13,340 (5,419) | 38,829 (20,063) | 91,526 (37,426) | 150,888 (52,505) | 215,019 (68,410) |
| Cumulative potency | 4,692 (2,625) | 9,735 (4,020) | 28,499 (13,649) | 67,112 (24,124) | 111,095 (33,502) | 158,237 (51,250) |
| Average dose | 1,135 (468) | 1,135 (450) | 1,127 (424) | 1,127 (401) | 1,096 (355) | 1,091 (312) |
| Average potency | 840 (416) | 829 (331) | 825 (283) | 825 (244) | 808 (223) | 805 (239) |
| Progestind,e | ||||||
| Cumulative dose | 125 (158) | 256 (278) | 716 (721) | 1,651 (1,337) | 2,716 (1,711) | 3,796 (2,443) |
| Cumulative potency | 146 (143) | 305 (247) | 879 (652) | 2,045 (1,166) | 3,411 (1,461) | 4,922 (1,960) |
| Average dose | 22 (27) | 22 (23) | 21 (20) | 20 (16) | 20 (13) | 19 (12) |
| Average potency | 26 (25) | 26 (21) | 26 (17) | 25 (14) | 25 (11) | 25 (9) |
| Percentages | ||||||
| Current OC use | 4 | 5 | 10 | 18 | 35 | 57 |
| Ever estrogen type usef | ||||||
| Mestranol | 31 | 36 | 41 | 49 | 55 | 54 |
| Ethinyl estradiol | 49 | 56 | 64 | 71 | 78 | 84 |
| Missing type | 20 | 14 | 11 | 7 | 7 | 8 |
| Ever progestin type usef | ||||||
| First generationg | 58 | 65 | 71 | 76 | 80 | 76 |
| Second generationh | 23 | 28 | 36 | 42 | 46 | 54 |
| Missing type | 20 | 14 | 11 | 7 | 7 | 8 |
| Number of OC brands used | ||||||
| 1 brand | 80 | 68 | 52 | 37 | 23 | 13 |
| 2 brands | 1 | 17 | 27 | 33 | 33 | 30 |
| 3 brands | 0 | 0 | 7 | 13 | 20 | 22 |
| 4 or more brands | 0 | 0 | 2 | 5 | 12 | 19 |
| Unknowni | 20 | 14 | 13 | 12 | 13 | 15 |
Values are standardized to the age distribution of the study population
N=9750 women missing cumulative and average estrogen dose and N=16,014 women missing cumulative and average estrogen potency
Units are as follows: cumulative estrogen dose: μg; cumulative estrogen potency: μg ethinyl estradiol equivalents; average estrogen dose: μg per month; average estrogen potency: μg ethinyl estradiol equivalents per month
N=9750 women missing cumulative and average progestin dose and N=16,013 women missing cumulative and average progestin potency
Units are as follows: cumulative progestin dose: mg; cumulative progestin potency: mg norethindrone equivalents; average progestin dose: mg per month; average progestin potency: mg norethindrone equivalents per month
Percentages can sum to more than 100% as women could have used both estrogen or progestin types
First generation progestin includes norethindrone, norethynodrel, norethindrone acetate, ethynodiol diacetate, medroxyprogesterone acetate, and chlormadinone acetate
Second generation progestin includes levonorgestrel and norgestrel
Women were included in the unknown number of brands category if they reported an ‘unknown OC brand’ at least once on the baseline questionnaire