By Piriya Mahendra
Women who last give birth after the age of 30 years have a decreased risk for endometrial cancer, researchers report in the American Journal of Epidemiology.
Each 5-year delay in last birth after the age of 30 years decreased the risk for endometrial cancer by approximately 13 percentage points, report Veronica Setiawan (University of Southern California, Los Angeles, USA) and team.
Indeed, women who last gave birth when they were 40 years or older had a 44% lower risk for endometrial cancer than women who gave birth to their last child before 25 years of age.
Women who had their youngest child between the ages of 30 and 34 years had a 17% reduced risk for endometrial cancer compared with those aged younger than 25 years, and women aged between 35 and 39 years had a 32% reduced risk.
The association between age at last birth and risk for endometrial cancer was similar across the four age-at-diagnosis groups: younger than 50 years, 50-59 years, 60-69 years, and 70 years or older, at respective odds ratios (ORs) of 0.81, 0.87, 0.88, and 0.89. This "shows that the protection persists for many years," commented Setiawan in a press statement.
The association was also persistent across White and Asian women, but not in the small subset of Black women in the study. Setiawan suggested that this warrants additional study of larger groups of Black women.
Further analysis revealed that older age at last birth was associated with a reduced risk for both types of endometrial cancer, at an OR of 0.87 for type I tumors and 0.90 for type II tumors.
"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," remarked Setiawan.
Several potential mechanisms underlying the association between advanced childbearing age and reduced risk for endometrial cancer have been suggested, she noted. Women capable of becoming pregnant at an older age may have a healthy endometrium. Prolonged exposure to progesterone during pregnancy may also protect against cancer development later in life during the critical stage for cancer development.
Alternatively, the association could be explained by the shedding of premalignant or malignant cells of the uterine cavity's mucosal lining, which are more likely to exist at an older age, during 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," said Setiawan.
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