# Cancer risk after preeclampsia: a cohort study in two Nordic populations

## TL;DR

Women who experience preeclampsia may have a lower risk of certain cancers later in life, according to a study in Nordic populations.

## Contribution

This study provides new evidence from large Nordic cohorts on the relationship between preeclampsia and cancer risk.

## Key findings

- Preeclampsia was linked to reduced cancer risk in Swedish women but not in Finnish women.
- Breast, cervical, and lung cancer risks were lower in both cohorts, while endometrial cancer risk was higher.
- Swedish siblings of preeclampsia-affected women also showed a reduced lung cancer risk.

## Abstract

Limited evidence suggests that preeclampsia (PE) is associated with reduced cancer risk later in life. We aimed to investigate this using large registry-based cohorts. We hypothesised that enhanced immune activation in PE women, suggested by autoimmune-type reactivity, lowers their subsequent cancer risk.

Utilising Medical Birth Registry data from Sweden and Finland, we identified 123,495 women with PE and 3,223,537 women without. Data were cross-linked to the national Cancer Registries. Incidence rate ratios with 95% CIs were calculated and adjusted for maternal birth year, age at first birth, and parity.

Overall cancer risk was significantly lower in Swedish PE women (IRR 0.91) but not in Finnish. Lower IRRs in PE women were found in both cohorts for breast (IRR 0.90 and 0.91), cervical (IRR 0.79 and 0.55) and lung cancer (IRR 0.72 and 0.63), while endometrial cancer showed increased incidence (IRR 1.28 and 1.46). Foetal sex had no impact on cancer risk. Among Swedish siblings to PE women, a slight reduction in cancer risk, driven by lower lung cancer incidence (IRR 0.86), was noted.

Our data show a link between PE and subsequent cancer risk, suggesting that shared mechanisms may predispose to PE and influence cancer development.