Table 3.

Associations between age at first full-term pregnancy, number of full-term pregnancies, and breast cancer risk, stratified by breastfeeding status (ever/never), among parous women ages 55 to 64 years in the Women's CARE Study and by ERPR status

All parous women
ERPR positive
ERPR negative
Never breastfed
Ever breastfed
Never breastfedEver breastfedNever breastfedEver breastfed
n (case/control)OR (95% CI)n (case/control)OR (95% CI)n (cases)OR (95% CI)n (cases)OR (95% CI)n (cases)OR (95% CI)n (cases)OR (95% CI)
All parous women 600/5551.00717/7930.87 (0.74-1.02)*2911.00345/7930.84 (0.68-1.03)1131.001370.84 (0.63-1.12)
    Age at first <25 y418/4271.00552/6490.90 (0.75-1.08)1901.00253/6490.91 (0.71-1.15)851.001120.82 (0.60-1.14)
    Age at first ≥25 y182/1281.00165/1440.62 (0.43-0.89)1011.0092/1440.57 (0.37-0.87)281.00250.65 (0.33-1.27)
Age first full-term pregnancy (y)
    <20139/1611.00265/2931.00551.00110/2931.00321.00611.00
    20-24279/2661.21 (0.90-1.64)287/3560.87 (0.67-1.13)1351.34 (0.63-1.64)143/3560.86 (0.61-1.20)531.12 (0.33-1.35)510.79 (0.50-1.25)
    25-29128/831.86 (1.25-2.78)118/1071.12 (0.77-1.63)712.32 (0.83-2.53)71/1071.25 (0.79-1.97)191.41 (0.37-2.08)181.03 (0.52-2.04)
    ≥3054/451.47 (0.88-2.45)47/371.05 (0.62-1.79)301.97 (0.82-4.11)21/370.86 (0.44-1.69)91.44 (0.69-6.15)71.10 (0.41-2.92)
Ptrend0.010.740.0030.810.200.99
Pheterogeneity ERPR-positive vs ERPR-negative0.460.71
Pheterogeneity ever vs never breastfed0.320.66
No. full-term pregnancies
    1113/951.0070/521.00551.00311.00151.00101.00
    2194/1671.02 (0.71-1.47)195/1830.82 (0.53-1.25)1041.12 (0.72-1.75)1110.95 (0.56-1.61)331.56 (0.77-3.14)361.23 (0.56-2.71)
    3153/1341.02 (0.69-1.50)176/2110.66 (0.42-1.01)751.06 (0.65-1.74)820.62 (0.36-1.07)362.21 (1.06-4.61)320.94 (0.42-2.11)
    ≥4140/1590.90 (0.61-1.35)276/3470.61 (0.40-0.93)570.85 (0.50-1.44)1210.58 (0.34-0.99)291.50 (0.69-3.25)590.89 (0.41-1.93)
Ptrend0.580.0070.410.0040.320.32
Pheterogeneity ERPR-positive vs ERPR-negative0.110.35
Pheterogeneity ever vs never breastfed0.330.29
  • NOTE: Unconditional logistic regression used to calculate OR and 95% CI; models include categories of age, race, study site, education, age at menarche, family history of breast cancer, age at first full-term pregnancy, and number of full-term pregnancies.

  • * OR of ever breastfeeding compared with parous women who have never breastfed.