Maternal reproductive hormones and angiogenic factors in pregnancy and subsequent breast cancer risk.

Breast cancer risk associated with pregnancy characteristics may be mediated by maternal hormones or angiogenic factors. We conducted a prospective breast cancer case-control study among women in the Avon Longitudinal Study of Parents and Children (ALSPAC) and Norwegian Mother and Child Cohort Study (MoBa) related to maternal pregnancy prolactin (n = 254 cases and 374 controls), placental growth factor (PlGF, n = 252 and 371), soluble fms-like tyrosine kinase-1 (sFlt-1, n = 118 and 240) and steroid hormone concentrations (ALSPAC only, n = 173 and 171). Odds ratios (OR) and 95% confidence intervals (CI) for a 1 SD change in analytes were estimated using unconditional logistic regression with matching factors (cohort, mother's birth year, serum/plasma, blood collection timing) and gestational age. Breast cancer ORs (95% CI) were 0.85 (0.51-1.43) for estradiol, 0.86 (0.67-1.09) for testosterone, 0.89 (0.71-1.13) for androstenedione, 0.97 (0.71-1.34) for hCG, 0.93 (0.75, 1.15) for prolactin, 1.00 (0.78-1.27) for PlGF and 1.91 (1.00-3.65 ALSPAC) and 0.94 (0.73-1.21 MoBa) for sFlt-1, and were similar adjusting for potential confounders. Results were similar by blood collection timing, parity, age at first birth or diagnosis, and time between pregnancy and diagnosis. These data do not provide strong evidence of associations between maternal hormones or angiogenic factors with subsequent maternal breast cancer risk.