Delaying childbirth may lower a woman's risk for ovarian cancer, according to a new study from the University of Southern California. Researchers found that women who waited until they were in their mid-30s to have their first child had a lower risk of ovarian cancer than those who had children earlier.

The study included almost 1,700 women in the Los Angeles area who had ovarian cancer, and about 2,300 women from the same geographical area who did not have ovarian cancer.

According to a Live Science article, each five-year delay in giving birth to her first child lowers a woman's risk of ovarian cancer by 16 percent: Women who were at least 35 years old when they gave birth to their first child had a 46 percent lower risk of ovarian cancer than women who first gave birth when they were younger than 20.

Researchers aren't sure why having a first baby later in life reduces risk. But they know that regular ovulation causes damage to ovaries, and theorize that the increase in progesterone during pregnancy causes some of the damaged cells that have built up over time to self-destruct. A later pregnancy could cause the elimination of a greater number of damaged cells.

"If you have a later age at first birth, you essentially are able to clear more of the malignancy-transformed cells," said study researcher Alice Lee, a doctoral student at the University of Southern California.

The study could mean good news for women who delay having children, which is becoming increasingly common.

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