Table 1.
Characteristica | Menstrual Cycle Length, days |
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<25 |
25–26 |
27–29 |
30–31 |
32–33 |
≥34 |
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No. | % | Mean | No. | % | Mean | No. | % | Mean | No. | % | Mean | No. | % | Mean | No. | % | Mean | |
No. of women | 116 | 229 | 1,482 | 589 | 121 | 116 | ||||||||||||
Age, years | 28.5 | 29.4 | 28.8 | 28.4 | 27.5 | 27.8 | ||||||||||||
Partner’s age, years | 31.2 | 31.8 | 30.9 | 30.9 | 30.6 | 30.5 | ||||||||||||
Age at menarche, years | 12.9 | 13.0 | 12.9 | 13.0 | 12.8 | 12.9 | ||||||||||||
Body mass index, kg/m2 | 24.6 | 24.1 | 24.0 | 24.2 | 23.7 | 25.0 | ||||||||||||
Physical activity, MET-hours/week | 27.9 | 26.2 | 24.3 | 25.4 | 24.4 | 23.7 | ||||||||||||
No vocational training | 12.3 | 9.7 | 11.3 | 12.6 | 10.9 | 13.2 | ||||||||||||
Parous | 32.4 | 30.8 | 35.8 | 36.1 | 41.0 | 27.7 | ||||||||||||
Current regular smoker, yes | 18.1 | 16.2 | 13.2 | 11.5 | 11.4 | 9.4 | ||||||||||||
Pack-years of ever smoking | 2.9 | 2.8 | 2.2 | 2.0 | 2.1 | 2.3 | ||||||||||||
Mother smoked during pregnancy, yes | 39.8 | 37.1 | 32.8 | 36.8 | 30.3 | 29.7 | ||||||||||||
Alcohol intake (current), drinks/week | 3.2 | 2.5 | 2.9 | 3.0 | 2.4 | 2.6 | ||||||||||||
Caffeine intake (current), mg/day | 109.0 | 110.3 | 109.1 | 101.6 | 105.1 | 108.8 | ||||||||||||
Frequency of intercourse, ≥4 times/week | 21.1 | 25.5 | 18.6 | 20.4 | 15.3 | 17.8 | ||||||||||||
Last method of contraception | ||||||||||||||||||
Barrier methods | 27.3 | 28.7 | 28.8 | 29.4 | 43.9 | 31.1 | ||||||||||||
Hormonal contraceptives | 66.0 | 60.7 | 61.2 | 58.9 | 46.3 | 60.6 | ||||||||||||
Withdrawal, charting, or other | 6.7 | 10.6 | 10.0 | 11.7 | 9.8 | 8.3 | ||||||||||||
Time to cycle regularity, years | 2.2 | 2.2 | 2.2 | 2.6 | 3.1 | 3.9 | ||||||||||||
Duration of flow ≥7 days | 4.5 | 3.5 | 2.9 | 4.1 | 5.1 | 4.2 | ||||||||||||
Amount of flow heavy or very heavy | 17.3 | 15.9 | 17.9 | 19.7 | 16.4 | 17.3 |
Abbreviation: MET, metabolic equivalent.
All characteristics, with the exception of age, are age standardized to the cohort at baseline.