Ovarian cancer is one of the deadliest cancers for women worldwide, especially in East Asian countries where the numbers continue to rise year after year.
In an attempt to understand the reasons for this increase, Korean researchers conducted a study involving more than two million women in their forties and older, to explore the relationship between a woman's reproductive history and her risk of developing ovarian cancer, across four different generations from the thirties to the sixties.
The findings, published in the journal JAMA Network Open, revealed that women who had more children had a lower risk of developing ovarian cancer, particularly among older generations where large families were prevalent.
But what is striking is that this protective effect has declined significantly or disappeared entirely among younger generations who have fewer children, suggesting that women today may not have the same protection that protected their grandmothers from ovarian cancer simply by having many children.
South Korea has experienced one of the fastest fertility declines in the world, with the average number of children per woman dropping from more than four in the 1970s to less than one in 2022. This sharp demographic shift offers scientists a rare opportunity to study how declining fertility affects cancer patterns in record time
But family size wasn't the only factor researchers considered. Data revealed that other aspects of a woman's reproductive history also play significant roles in determining her risk. Women who started menstruating early, at age 12 or younger, were more susceptible, and a longer reproductive lifespan generally increases the likelihood of developing the disease.
In contrast, researchers found that the use of birth control pills significantly reduces the risk in premenopausal women, but offers little protection to postmenopausal women, and that hormone therapy after menopause clearly increases the risk.
The study compared women born in four different decades, from their thirties to their sixties, and found that having two or more children reduces the risk of developing the disease by about a third overall, but this reduction was less pronounced among younger women born in their sixties. It also showed that the effect of birth control pills varies with age; they are very beneficial for women before menopause but lose their protective effectiveness afterward.
The researchers conclude their study by emphasizing that understanding these factors helps doctors assess risks more accurately and provide personalized preventive advice for each woman based on her reproductive history and age, especially in light of the changing fertility landscape around the world.
