LEVELS OF MATERNAL SERUM ALPHA-FETOPROTEIN (AFP) IN PREGNANT-WOMEN AND SUBSEQUENT BREAST-CANCER RISK

High maternal serum alpha-fetoprotein (AFP) levels during pregnancy ma y be instrumental in reducing the subsequent risk of breast cancer. Th is hypothesis was tested in a nested case-control study using stored f rozen sera accrued between 1959 and 1966 by the University of Californ ia at Berkeley Child Health and Development Studies (CHDS) group from a cohort of pregnant women. Cases with histologically confirmed breast cancer were identified from California Cancer Registry files covering their date of enrollment in the CHDS until 1994. Controls were select ed from the CHDS cohort by using randomized recruitment. Third-trimest er maternal serum AFP levels were analyzed by using both a radioimmuno assay and an immunoenzymatic method. After controlling for multiple co nfounders in logistic regression models, the authors found an inverse association between high levels of maternal serum AFP (top quartile) d uring the index pregnancy and the risk of breast cancer. The protectiv e effect of high levels of maternal serum AFP varied by age at first f ull-term pregnancy (age 20 years or less: odds ratio (OR) = 0.43, 95% confidence interval (CI) 0.28-0.65; age 21-23 years: OR = 0.62, 95% CI 0.41-0.92). After age 27 years, the estimated risk exceeded unity (OR = 1.67, 95% CI 1.14-2.45), These study findings suggest that some of the protection against breast cancer conferred by early first full-ter m pregnancy may result from high levels of maternal serum AFP. After a ge 27 years, a high maternal serum AFP level is not protective and may increase risk.