Is absorption of oral contraceptives affected by intestinal bypass for obesity?

QUESTION: Please discuss the effectiveness of oral contraceptives in women who have undergone intestinal bypass surgery for obesity. Is there sufficient steroid absorption to prevent pregnancy? ANSWER: I am not aware of any data on the absorption of oral contraceptives in patients with an intestinal bypass. The effectiveness of oral contraceptives depends on the amount of estrogen and progestin administered, and decreasing the dosage to too low a level will increase the likelihood of pregnancy. Since the bypass will substantially reduce the absorptive area, it is quite possible that effective steroid absorption would not be obtained. In the absence of a study demonstrating adequate steroid absorption in this type of patient, in my opinion a contraceptive procedure other than oral contraceptives should be advised.