A recent study has found that overweight or obesity increases the chances of pregnancy while using birth control pills. Gynecologists say that birth control pills (also known as oral contraceptives) have not enough effect on overweight or obese women. Overweight (BMI 25 to 29.9) women have 60% and obese (BMI 30 or more) women have 70% more chances of pregnancy than normal weight (BMI 18.5 to 24.9) women while taking oral contraceptives regularly. For women who missed oral contraceptive, the risk of pregnancy more than doubled compare to overweight or obese women. Study says that out of hundred overweight women taking the oral contraceptives, five got pregnant while only three out of hundred normal weight women who take oral contraceptives got pregnant each year.

The reason of failure of oral contraceptives is not clearly known. This is a big research area. They said there are several possibilities for failure of oral contraceptives in obese women.