Pregnancy reduces the risk of cancer of the endometrium, the uterine mucosa, and the protective effect increases depending on the number of pregnancies, researchers from Bristol University have found, BMC Medicine journal published.
Endometrial cancer is a dangerous disease, the sixth most common cancer in women. It kills hundreds of thousands of people each year, and the number of new cases is increasing worldwide, particularly in developing countries, where women are having fewer and later children.
The study used data from 270,000 British Biobank (UKBB) women. All of them were of European origin.
Overall, the risk of developing endometrial cancer was inversely proportional to the number of successful pregnancies. Women who gave birth to three children had half the risk compared to those who did not. Some protective effect was also observed if the pregnancy ended in miscarriage or infant death.
The protective effect of childbirth may be due to the oncogenic effect of estrogen, which is counteracted by progesterone. Progesterone levels remain high throughout pregnancy. Oral contraceptives containing progesterone also reduce the risk of endometrial cancer, the study found. This confirms that the ratio of estrogen to progesterone is associated with the risk of developing endometrial cancer.
Interestingly, the large number of abortions in women's medical histories had a greater protective effect than childbirth. This may be due to a more rapid increase in progesterone levels compared to pregnancy.
The study showed for the first time that the number of pregnancies may have a protective effect on endometrial cancer risk. Further studies are needed to confirm the scientists' findings.