Background: Pregnancy-related hypertensive disorders, including preeclampsia (PE) and pregnancy-induced hypertension (PIH), may influence the maternal risk of breast cancer. However, results of the cohort studies were inconsistent.
Methods: An updated meta-analysis of cohort studies was performed to evaluate the association between PE, PIH and maternal breast cancer incidence. Relevant studies were identified via searching of PubMed and Embase databases. A random effect model was applied to synthesize the results. Stratified analyses were performed to evaluate the potential influence of parity, gender of offspring, and study design on the association between PE and maternal breast cancer incidence.
Results: Ten cohort studies with 2,417,899 pregnant women were included. Maternal risk of breast cancer was not significantly affected by PE (risk ration [RR] = 0.93, 95% confidence interval [CI]: 0.82-1.06, p = .27), or PIH (RR = 0.95, 95% CI: 0.81-1.12, p = .54). Interestingly, PE was associated with significantly lowered maternal incidence of breast cancer in women who give birth to male offspring (RR = 0.79, p < .01), and in those of prospective cohort studies (RR = 0.87, p < .01). However, no significant association between PE and maternal breast cancer was detected in primiparous women, those who gave birth to female offspring, or those of retrospective cohorts.
Conclusions: Current evidence did not support a conclusive association between PE, PIH and the maternal risk of breast cancer. Gender of the offspring may influence the association between PE and maternal breast cancer incidence.
Keywords: Preeclampsia; breast cancer; cohort study; meta-analysis; pregnancy-induced hypertension.