(RxWiki News) Women are having babies and growing their families later in life. In terms of one cancer risk, being older is helpful.
Women who give birth after the age of 40 have a significantly lower risk of endometrial or uterine cancer than younger mothers. These are the findings of an international study.
"Ask your gynecologist about cancer screenings."
Endometrial cancer invades the tissue lining the uterus - the endometrium. This is the most common gynecological cancer in the US and is diagnosed in about 47,000 women each year.
Veronica "Wendy" Setiawan, PhD, assistant professor of preventive medicine at the Keck School of Medicine of the University of Southern California (USC), led the study.
"While childbearing at an older age previously has been associated with a lower risk of endometrial cancer, the size of this study definitively shows that late age at last birth is a significant protective factor after taking into account other factors known to influence the disease — body weight, number of kids and oral contraceptive use," Dr. Setiawan said.
Thought to be the largest of its kind, the study analyzed data from 17 different studies, involving nearly 8,700 women with endometrial cancer and 16,562 health women who served as controls.
Researchers found that cancer risks began to decline for women who gave birth after age 30. When compared to women whose last birth was before age 25, women who had babies between 30 and 34 had a 17 percent lower risk; between the ages of 35 and 39, the risk was reduced by 32 percent; after age 40, the risk was lowered 44 percent.
This protective effect lasts for many years - into a woman's 70s, the researchers learned.
The effect was consistent in both Caucasian and Asian women, but wasn't seen in the small number of black women in the study, which suggests the need for additional research.
For now, Dr. Setiawan believes this effect may be due to three factors - older women who become pregnant tend to have a healthy uterus and fewer menstrual periods without ovulation; exposure to the hormone progesterone could be especially helpful to older women and pre-cancerous and malignant cells are shed with childbirth.
"This study shows an important protective factor for endometrial cancer, and when the exact mechanism by which it protects women from getting the disease is known, it can help our understanding of how endometrial cancer develops and thus how to prevent it," Dr. Setiawan said.
This research was published July 23 in the American Journal of Epidemiology.
Grants from the National Cancer Institute of the National Institutes of Health supported this work.
No conflicting interests were reported.