Women with preeclampsia may have reduced risk of breast cancer: a meta-analysis of cohort studies with 7.8 million participants.

This review pooled data from the literature to examine the association between preeclampsia (PE) and subsequent risk of breast cancer in women. Cohort studies published in the databases of PubMed, Embase, Scopus, and Web of Science up to 18 July 2023 were searched. Adjusted data were pooled to obtain the risk ratio (RR). Eleven studies with 15 cohorts and a cumulative sample size of 7,838,693 women were included. Meta-analysis of all studies demonstrated a reduced risk of breast cancer in women with PE as compared to those without PE (RR: 0.89 95% CI: 0.83, 0.95 p  < 0.001 I2  = 50%). Follow-up ranged from 8 to 29.2 years. Results did not change during sensitivity analysis. Outcomes varied on subgroup analysis based on location, study type, data extraction method, incidence of breast cancer, and follow-up. To conclude, women with PE may have a reduced risk of breast cancer later in life. However, the risk reduction is minimal and may not have much clinical significance. The evidence is also limited by high inter-study heterogeneity and lack of adjustment of all possible confounders.