Table 2.
No. of Pregnancies | No. of Cycles | Unadjusted Model |
Adjusted Modela |
|||
FR | 95% CI | FR | 95% CI | |||
Menstrual cycle length, days | ||||||
<25 | 65 | 646 | 0.60 | 0.46, 0.78 | 0.64 | 0.49, 0.84 |
25–26 | 152 | 996 | 0.92 | 0.77, 1.11 | 0.94 | 0.77, 1.13 |
27–29 | 1,051 | 6,411 | 1.00 | Referent | 1.00 | Referent |
30–31 | 416 | 2,321 | 1.10 | 0.97, 1.25 | 1.10 | 0.97, 1.25 |
32–33 | 92 | 419 | 1.40 | 1.10, 1.78 | 1.35 | 1.06, 1.73 |
≥34 | 87 | 467 | 1.17 | 0.92, 1.50 | 1.17 | 0.91, 1.49 |
Age at menarche, years | ||||||
<12 | 245 | 1,424 | 1.04 | 0.89, 1.22 | 1.06 | 0.91, 1.24 |
12–13 | 1,056 | 6,420 | 1.00 | Referent | 1.00 | Referent |
14 | 376 | 2,158 | 1.07 | 0.94, 1.22 | 1.05 | 0.92, 1.20 |
≥15 | 186 | 1,258 | 0.89 | 0.75, 1.05 | 0.88 | 0.74, 1.05 |
Time until cycle regularity, years | ||||||
<2 | 933 | 5,365 | 1.00 | Referent | 1.00 | Referent |
2–3 | 592 | 3,719 | 0.90 | 0.80, 1.02 | 0.90 | 0.80, 1.02 |
≥4 | 338 | 2,176 | 0.89 | 0.78, 1.03 | 0.89 | 0.77, 1.03 |
Duration of menses, days | ||||||
<3 | 150 | 1,048 | 0.86 | 0.71, 1.04 | 0.87 | 0.72, 1.05 |
3–4 | 1,006 | 5,921 | 1.00 | Referent | 1.00 | Referent |
5–6 | 636 | 3,938 | 0.94 | 0.84, 1.05 | 0.92 | 0.82, 1.02 |
≥7 | 71 | 353 | 1.19 | 0.91, 1.56 | 1.14 | 0.87, 1.51 |
Intensity of menstrual flow | ||||||
Light (≤10 pads/tampons) | 449 | 2,814 | 0.94 | 0.83, 1.07 | 0.95 | 0.84, 1.09 |
Moderate (11–20 pads/tampons) | 1,079 | 6,320 | 1.00 | Referent | 1.00 | Referent |
Heavy (21–30 pads/tampons) | 313 | 1,936 | 0.91 | 0.76, 1.09 | 0.90 | 0.74, 1.08 |
Very heavy (>30 pads/tampons) | 22 | 190 | 0.76 | 0.47, 1.22 | 0.70 | 0.43, 1.13 |
Menstrual flow and duration | ||||||
Light/moderate, <5 days | 1,052 | 6,263 | 1.00 | Referent | 1.00 | Referent |
Light/moderate, ≥5 days | 104 | 706 | 0.84 | 0.66, 1.07 | 0.84 | 0.65, 1.09 |
Heavy/very heavy, <5 days | 476 | 2,871 | 0.97 | 0.86, 1.10 | 0.95 | 0.84, 1.09 |
Heavy/very heavy, ≥5 days | 231 | 1,420 | 0.94 | 0.77, 1.13 | 0.90 | 0.74, 1.09 |
Abbreviations: CI, confidence interval; FR, fecundability ratio.
Adjusts for age, body mass index, smoking, intercourse frequency, last method of contraception, and menstrual cycle length (when applicable).