USC (US) — Women who have their last baby in their 30s and 40s have a reduced risk of developing endometrial cancer, the most common gynecological cancer in the US.
New research finds that women who last give birth at age 40 or older have a 44 percent decreased risk of endometrial cancer, which strikes the tissue lining of the uterus, as compared to women who have their last baby younger than 25.
The study found that risk begins to decrease after age 30 by approximately 13 percentage points for each five-year delay in last births. Compared to women who last give birth before age 25, those who have their last child between age 30 and 34 reduce their risk by 17 percent and those between age 35 and 39 reduce their risk by 32 percent.
“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,” says Veronia “Wendy” Setiawan, assistant professor of preventive medicine at the Keck School of Medicine at the University of Southern California.
Published online in the American Journal of Epidemiology, the study that is believed to be the largest of its kind, examined pooled data from four cohort studies and 13 case-control studies. Funded by the National Cancer Institute, the research examined a total of 8,671 cases of endometrial cancer and 16,562 control subjects, all derived from studies in the Epidemiology of Endometrial Cancer Consortium.
“We found that the lower risk of endometrial cancer continued for older mothers across different age-at-diagnosis groups, including under 50, 50-59, 60-69, and over 70—which shows that the protection persists for many years,” Setiawan says.
“Protection also did not vary by the two types of the disease: the more common Type 1, which we think is related to estrogen exposure; and the more rare, but more aggressive and deadly, Type 2, which has been thought to develop independent of hormones.”
Endometrial cancer is the fourth most common cancer diagnosed among American women. The American Cancer Society estimates that in 2012 about 47,130 new cases of cancer of the uterine body will be diagnosed, and about 8,010 women will die from such cancers. The vast majority of those cases are endometrial cancer.
Setiawan’s research also examines whether the association between age at last birth and endometrial cancer was consistent across race and ethnicity. The protective association was observed in Caucasian and Asian women, but not in the study’s small subset of black women, warranting additional study of larger groups of those women.
More research is necessary to determine why late age at last birth might protect against endometrial cancer, but Setiawan notes that several potential mechanisms have been suggested by other investigators, including:
Women capable of becoming pregnant at an older age may possess a healthy endometrium or experience fewer menstrual cycles without ovulation
Prolonged exposure to the hormone progesterone during pregnancy may be especially beneficial at older ages, the critical period for endometrial cancer development
Premalignant or malignant cells of the uterine cavity’s mucosal lining, which are more likely to exist with increasing age, are shed during childbirth.
“This study shows an important protective factor for endometrial cancer,” Setiawan says, “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.”
The analysis was supported by the National Cancer Institute of the National Institutes of Health.
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— Last Edited by Greentea at 2012-07-26 08:31:05 —