Research from a study that was published in Obstetrics and Gynecology revealed that being overweight can make a woman's birth control pills less effective. According to the study, 5% of women who are considered overweight according to their body mass index (BMI) get pregnant every year on the pill while only 3% of women who have a normal BMI have unplanned pregnancies on birth control pills.
Why Those Extra Pounds May Make Birth Control Pills Less Effective
The study showed that the higher a woman's BMI, the less effective her birth control pills became. There are several different explanations that are being considered as the reason for birth control being less effective in overweight women.
Most birth control pills nowadays have approximately 20-35 mcg of estrogen, which is far less than the pill had just 10 years go. Pharmaceutical companies are making more low-dose pills to help with their unwanted side effects such as weight gain, acne, and headaches. Just like any type of medicine, the pill has to circulate through the woman's bloodstream, which means if a woman has more mass, the pill may not be able to circulate as needed to produce the utmost effectiveness.