Prenatal factors and infant feeding in relation to risk of benign breast disease in young women.

Benign breast disease (BBD) is a well-established risk factor for breast cancer, but little work has considered a girl's early life and her risk for BBD in adulthood. We investigated factors, from pre-conception through infant feeding practices, in relation to subsequent BBD risk in young women. The Growing Up Today Study (GUTS) includes 9032 females, born 1980-1987, who completed questionnaires annually from 1996 through 2001, then 2003, 2005, 2007, 2010, and 2013. In 1996, their mothers provided each participant's birth weight and length, gestational age, biological father's height, and infant feeding factors (e.g., breast-fed, type of formula). In 1999, their mothers reported maternal pre-pregnancy weight and weight gain during index pregnancy. Beginning in 2005, daughters (18 years+) reported whether they had ever been diagnosed with biopsy-confirmed BBD (n = 142 cases, through 2013). Logistic regression estimated associations between early life factors and biopsy-confirmed BBD. Girls whose mother's BMI prior to pregnancy was 20-25 kg/m(2) were at lower risk of BBD as young women (OR = 0.66, p = 0.04, vs. maternal pre-pregnancy BMI < 20). Girls whose mothers gained 20 + pounds (vs. <20 pounds) during pregnancy were at lower risk (among full-term singleton births: OR = 0.48, p = 0.007, if mother gained 20-35 pounds). However, neither birth weight nor BMI at birth were associated with subsequent BBD risk. We found no evidence that infant feeding practices were linked to BBD. A healthy maternal BMI before pregnancy and sufficient weight gain during pregnancy may produce daughters at lower risk for BBD as young women. Further examination of these findings is needed.