Birth Control Pills Makes Eggs Old Looking, But They Don't Affect a Woman's Fertility

According to a new study taking birth control pills may make an egg look old at least when assessed by two specific tests of fertility.

The finding suggests that in younger women on pill, hormone levels associated with the ability to make mature, healthy eggs are more like those of older women than the levels of younger women who don’t use these contraceptives. These women also have fewer structures in their ovaries that can mature into viable eggs.

But it doesn’t imply that the pill prematurely ages women’s eggs, the researchers said. Instead, it adds up to the observation that the pill obscures a woman’s underlying reproductive status.

“Women should not be freaking out that they are losing their eggs” if they’re taking birth control, said Lubna Pal, director of the menopause and polycystic ovarian syndrome programs at Yale University, who was not involved in the study. “These [tests] are yardsticks that should be applied only in the context of fertility assessments," quoted the Washington Post.

The "ovarian reserve" of a woman is a procedure which predicts the wellness of the ovaries to produce mature oocytes that can be fertilised. As women age, their ovarian reserve diminishes, leading to fewer eggs and to fewer that reach a mature stage.

Most physicians defiines the term 'ovarian reserve' by measuring the levels of anti-Mullerian hormone, or AMH, in the blood and also by making a vaginal ultrasound to count the number of ovarian follicles. When combined, these two markers show strong correlation with the way a woman’s ovaries age.

In this work, researchers looked at both markers in 833 Danish women between ages 18 and 46, including some who used oral contraceptives. Those who were taking the pill had 19 percent lower levels of AMH and 16 percent fewer early-stage follicles. Their ovaries were also much smaller than those of women who were not taking the pill.

The researchers confirmed that this doesn’t mean these women’s egg quality has permanently declined. Instead, hormonal birth control simply suspends the egg maturation process in an earlier stage. Once women stop taking birth control pills, they are usually able to conceive within a few months.