Table 3.

Association of perinatal factors with percent density for all women and by menopausal status at time of mammography

All women
Premenopausal women
Postmenopausal women
Full model
Full model
Full model
nAdj mean*Adj mean (95% CI)nAdj mean*Adj mean (95% CI)nAdj mean*Adj mean (95% CI)
Birthweight (kg)
    Continuous94017.619.4 (18.7-20.2)29932.132.1 (30.7-33.4)64115.616.5 (15.6-17.3)
    P trend0.010.010.430.53<0.0010.01
    <2.9520619.420.1 (19.0-21.2)6334.633.4 (31.1-35.7)14317.117.1 (15.9-18.3)
    2.95-3.3726220.121.0 (20.1-22.0)9832.031.4 (30.0-32.8)16419.819.8 (18.5-21.0)
    3.38-3.7424822.022.9 (21.8-24.0)7636.235.4 (33.2-37.5)17220.220.2 (18.9-21.4)
    3.75+22422.323.0 (21.8-24.1)6235.934.6 (32.6-36.6)16221.021.0 (19.7-22.3)
    P trend<0.01<0.010.160.19<0.01<0.01
    Don't know82719.820.6 (20.1-21.2)12331.030.4 (28.9-31.9)70419.319.3 (18.6-19.9)
Gestational age
    Preterm6218.519.2 (17.3-21.1)2132.830.5 (26.9-34.0)4116.316.7 (14.4-19.0)
    Term77321.122.0 (21.4-22.6)24533.833.3 (32.2-34.4)52820.320.2 (19.5-21.0)
    Postterm2723.123.7 (20.9-26.5)1133.934.7 (30.3-39.0)1623.323.0 (19.2-26.8)
    P trend0.070.070.680.250.040.07
    Don't know78019.820.7 (20.1-21.3)11832.831.6 (29.9-33.2)66218.918.9 (18.3-19.5)
    Missing12519.720.5 (19.1-22.0)2733.933.2 (30.9-35.6)9818.618.5 (16.8-20.1)
Eclampsia/preeclampsia
    No1,02920.721.5 (21.0-22.0)29133.532.7 (31.8-33.6)73819.919.9 (19.3-20.4)
    Yes1818.817.7 (14.5-20.9)536.135.5 (30.5-40.6)1317.014.6 (10.5-18.7)
    P0.630.250.690.610.490.16
    Don't know59620.020.7 (19.9-21.4)9933.532.9 (30.8-34.9)49718.918.7 (18.0-19.5)
    Missing12419.520.3 (18.9-21.8)2732.631.7 (29.2-34.1)9718.818.6 (17.0-20.2)
Jaundice
    No1,03520.321.2 (20.6-21.7)26333.532.6 (31.6-33.6)77219.319.4 (18.8-20.0)
    Yes2923.423.7 (20.5-26.8)837.433.1 (25.6-40.7)2122.121.6 (18.3-24.9)
    P0.170.270.400.890.280.39
    Don't know57420.521.4 (20.7-22.1)11933.933.0 (31.4-34.5)45519.519.6 (18.8-20.4)
    Missing12919.520.6 (19.1-22.0)3231.731.7 (29.2-34.2)9719.119.2 (17.5-20.9)
Breastfed as an infant
    No35220.220.9 (20.3-21.4)15833.833.1 (31.8-34.4)19418.518.2 (17.6-18.8)
    Yes91120.821.7 (20.8-22.6)15532.631.9 (30.6-33.3)75619.920.0 (18.9-21.1)
    P0.690.520.290.310.160.08
    Don't know38220.220.8 (19.9-21.6)8334.032.8 (30.8-34.8)29919.118.9 (17.9-19.8)
    Missing12219.720.6 (19.1-22.0)2633.232.0 (29.6-34.4)9618.918.8 (17.1-20.4)
  • * Means adjusted for age at mammography, weight at follow-up 1, HRT use, and menopausal status.

  • Means and 95% CIs, additionally adjusted for education, age at menarche, parity and age at first birth, oral contraceptive use, alcohol use, current smoking status and smoking history.