Mean arterial pressure, pregnancy induced hypertension, and preeclampsia: Evaluation as independent risk factors and as surrogates for high maternal serum alpha-protein in estimating breast cancer risk.

PURPOSE: Data from a nested case-control study were analyzed to examine high mean arterial pressure (MAP), hypertension of pregnancy and preeclampsia as independent predictors, and as surrogate markers for elevated Alpha-fetoprotein (AFP) levels in evaluating breast cancer risk. METHODS: Cases (n = 205) were identified by the California Cancer Registry from a cohort of pregnant women who were part of the Kaiser Health Plan and took part in the Child Health and Development Studies initiated by the University of California, Berkeley, from June 1959 to September 1966. Controls (n = 337) were selected by randomized recruitment from the same cohort probability matched to cases by distribution of birth dates of cases. RESULTS: High MAP was associated with breast cancer risk, and was different across quartiles of age at first full term pregnancy. Odds Ratios across quartiles were 0.24 (95% CI = 0.08–0.71), 0.84 (95% CI = 0.39–1.66), 1.00 (referent), and 2.50 (95% CI = 1.21–5.13). Neither diagnosed preeclampsia nor hypertension of pregnancy showed any association with breast cancer risk. When both high Alpha-fetoprotein and high mean arterial pressure were entered into the same analysis neither changed the odds ratio for the other more than eight percent. Additionally, AFP level was not a linear function of MAP. CONCLUSIONS: Although the pattern of odds ratios across quartiles of age at first full term pregnancy were similar for the two variables it can not be concluded that high MAP is an adequate surrogate for high levels of maternal serum AFP, but rather represents some related process which is in and of itself a risk factor for breast cancer.