Pregnancy loss is a common complication in early pregnancy, affecting around a third of all pregnancies. In more than half of all losses, the fetus has an abnormal number of chromosomes, explaining the loss. An additional unknown proportion may have other more discrete genetic abnormalities causing the loss. The mechanisms resulting in losses for the remaining women is unknown. Scientific evidence suggests that the mother’s immune system in some losses may be involved, possibly by recognizing the fetal cells as foreign and therefore rejecting them. As the immune system is important in continuously clearing abnormal cells, that could otherwise give rise to cancer, the group hypothesized that women experiencing pregnancy loss or subtypes of pregnancy loss, had an increased risk of cancer.
The study included 28,785 Danish women with cancer, and 283,294 controls without cancer and women were followed for up to 45 years. The research group examined if pregnancy loss was associated with 11 site-specific invasive cancers (breast, ovarian, endometrial, cervical, bladder, renal, lung, gastro-intestinal, brain, haematological, and melanoma) and all-type cancer. The study is unique, regarding the population size, the detailed information on subtypes of pregnancy loss and the many different cancer types investigated. Overall, the group did not find a link between increasing numbers of pregnancy loss, or subtypes of pregnancy loss, and long-term risk of cancer.
The findings are reassuring, as they indicate that women who experience pregnancy loss or subtypes of pregnancy loss, such as recurrent pregnancy loss, should not fear an increased risk of malignancy.
The study is one of many trying to increase our knowledge in why pregnancies, were the fetus has a normal number of chromosomes, still end in a loss. Current knowledge about the reasons are sparse, and the serious implications for women affected warrant further investigation.
The study was conducted by medical doctor and PhD-student Anders Mikkelsen, in collaboration with researchers and medical doctors from the Recurrent Pregnancy Loss Unit at the Fertility Clinic and The Department of Gynaecology at Rigshospitalet, Denmark. The study is published in The Lancet EClinicalMedicine and available here.
The study was funded by Rigshospitalet’s Research Foundation and Ole Kirk’s Foundation.
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