Surveillance data say yes, but possible confounders must be taken into account.
When used in real life, oral contraceptives (OCs) have higher failure rates than when used ideally (i.e., consistently and correctly). In a prospective nonintervention active-surveillance study that involved >52,000 U.S. women (mean age, 26), funded by the manufacturer of OCs that contain the progestin drospirenone, investigators compared the effectiveness of combination OCs by type of progestin and length of pill-free interval. Regimens were 24 or 21 days of drospirenone/estradiol plus 4 or 7 days of inactive pills, or 24 or 21 days of other progestins/estradiol plus 4 or 7 inactive-pill days.
During >73,000 woman-years of OC use, >1600 unintended pregnancies occurred. Life-table estimated failure rates at the end of 1 year were 2.1% for 24…