Table 1.
Characteristics of the study population by case status (means or percents)
| Controls | Cases | |
|---|---|---|
| N | 1807 | 814 |
| % in NHS I | 77% | 66% |
| % in NHS II | 23% | 34% |
| Mothers' pregnancy weight gaina | 23 | 23 |
| % in each weight gain categorya: | ||
| Gained <10 lbs | 4.9% | 4.2% |
| Gained 10–14 lbs | 15.7% | 14.9% |
| Gained 15–19 lbs | 22.8% | 24.1% |
| Gained 20–29 lbs | 36.4% | 35.8% |
| Gained 30–40 lbs | 14.7% | 16.9% |
| Gained 40+ lbs | 5.6% | 4.1% |
| Mothers' pre-pregnancy BMI(kg/m2)a | 21.3 | 21.4 |
| % in each BMI categorya: | ||
| BMI <20 | 31.2% | 31.4% |
| 20–22.4 | 42.8% | 39.4% |
| 22.5–24.9 | 18.8% | 21.9% |
| 25.0–29.9 | 6.0% | 6.5% |
| BMI ≥ 30 | 1.2% | 0.8% |
| Nurses' year of birth | 1940 | 1942 |
| Nurses' birthweight (lbs) | 7.4 | 7.5 |
| Mother smoked during pregnancy | 13% | 17% |
| Family history of breast cancerb | 14% | 22% |
| Nurses' age at menarche <12 years | 24% | 24% |
| Nurses' adult height (inches) | 65 | 65 |
| Nurses' BMI at age 18 | 21.3 | 20.8 |
a
Excluding those with missing data for that question.
b
Family history in mother or sister as reported by nurse.