A 21-year-old G0 presents to your office because her menses is 2 weeks late. She states that she is taking her birth control pills correctly; she may have missed a day at the beginning of the pack, but took it as soon as she remembered. She has no medical problems, but 3 weeks ago she had a “viral stomach flu,” and missed 2 days of work due to nausea, vomiting, and diarrhea. Her cycles are usually regular, even without oral contraceptive pills. She has been on the pill for 5 years, and recently developed some midcycle bleeding, which usually lasts about 2 days. She has been sexually active with the same partner for the past 3 months, and has a history of chlamydia 3 years ago. She has had a total of 10 sexual partners. A urine pregnancy test is positive.
Which of the following is the major cause of unplanned pregnancies in women using oral contraceptives?a. Breakthrough ovulation at midcycle
The pregnancy rate with birth control pills, based on theoretical effectiveness, is 0.1%. However, the pregnancy rate in actual use is 0.7%. This increase is typically due to incorrect use of the pills. Breakthrough ovulation on combination birth control pills, when the pills are taken correctly, is thought to be a very rare occurrence. Unintended pregnancy in women correctly using oral contraceptive pills is not related to sexual frequency, gastrointestinal disturbances, or the development of antibodies.