Cancer diagnosis among women with recurrent pregnancy loss: a retrospective cohort study

Research question: What is relationship between unexplained recurrent pregnancy loss (RPL) and risk of cancer morbidity? Design: A retrospective observational cohort study was conducted, based on data from a tertiary medical centre. RPL cases (exposed) were defined as women presenting with three or more unexplained confirmed pregnancy losses at 5-24 weeks, whose first visit to the RPL clinic was between 1990 and 2010. The unexposed group included women giving birth who were not RPL patients; these were matched by age and year of giving birth/admission (1:5 ratio). Data from the RPL and the live birth registries were cross-linked to the Israeli national cancer registry according to the unique ID number and merged into one database. Results: The study group comprised 937 RPL patients who were matched by maternal age (P = 1.0) and admission date (P = 0.84) to 4685 women achieving a live birth. There was no difference in overall cancer incidence between groups (adjusted odds ratio [OR] 0.76, 95% confidence interval [CI] 0.55-1.03; P = 0.08). The secondary RPL group showed a trend towards decreased cancer morbidity incidence compared with primary RPL (adjusted OR 0.65, 95% CI 0.41-1.03; P = 0.07). Analysis by cancer type showed a similar risk for breast cancer among women with RPL compared with live birth, but a significantly lower risk for gynaecological cancers among women with RPL (adjusted OR 0.25, 95% CI 0.08-0.7 9; P = 0.018). Conclusions: Unexplained RPL may be related to a lower risk of gynaecological cancers, possibly explained by hyper responsive immunological mechanisms involving uterine natural killer cells.