Unintended pregnancies are a recognized occurrence among women using oral contraceptives (OCs) as a consequence of both user and method failure. However, OCs also influence the occurrence of unintended pregnancies through an additional, poorly recognized, route: cessation of OC use by women who do not wish to become pregnant but stop using OCs because of side effects or other reasons. Many such women fail to immediately substitute a new contraceptive and/or adopt a less reliable contraceptive. This is a particularly important consideration for the approximately 3.7 million women who begin taking OCs in the United States each year since this group commonly experiences side effects and has a high discontinuation rate. Using a decision tree to follow a cohort of OC users over one year, we estimate that over 1 million unintended pregnancies are related to OC use, misuse or discontinuation. The greatest proportion of these, 61%, occur in women who discontinue OCs; of these, 66.6% occur in women who fail to immediately substitute other contraceptives and 33.3% because of the adoption of less reliable contraceptive methods. Of continuing OC users, the majority, exhibiting good compliance, contribute 24% of pregnancies because of their large numbers. Continuing OC users who are poor compliers, though many fewer, are responsible for 15% due to their high pregnancy rate. Unintended pregnancies in women who discontinue OCs account for approximately 20% of the 3.5 million annual unintended pregnancies in the United States, incurring costs of nearly +2.6 billion.(ABSTRACT TRUNCATED AT 250 WORDS)
PIP: Findings from clinical trials and a survey of 10,000 users of oral contraceptives (OCs) formed the basis for developing a decision tree or chart that reproductive medicine specialists used to follow a cohort of OC users annually. They used a sensitivity analysis to estimate that OC use, misuse, or discontinuation are associated with 1,045,000 unintended pregnancies in the US each year. 61% of these unintended pregnancies occur to women who discontinue OCs. About 20% of women who discontinue OCs do not immediately adopt another contraceptive method. 33.3% occur because the women substituted OCs with less reliable contraceptive methods. Continuing OC users with good compliance account for 24% of the unintended pregnancies. Continuing OC users with poor compliance make up 15% of unintended pregnancies. Their number was much lower than that of good compliers (2.05 vs. 11.6 million). If all women used OCs correctly, about 687,000 unintended pregnancies would not occur. Physicians need to stress the need for immediate adoption of another reliable contraceptive if OC use is discontinued and the patient does not wish to conceive. They should counsel new OC adopters to expect side effects (e.g., bleeding) and that these side effects are temporary. This should reduce OC discontinuation.