Postfertilization effects of oral contraceptives and their relationship toinformed consent

The primary mechanism of oral contraceptives is to inhibit ovulation, but t his mechanism is not always operative. When breakthrough ovulation occurs, then secondary mechanisms operate to prevent clinically recognized pregnanc y. These secondary mechanisms may occur either before or after fertilizatio n. Postfertilization effects would be problematic for some patients, who ma y desire information about this possibility. This article evaluates the ava ilable evidence for the postfertilization effects of oral contraceptives an d concludes that good evidence exists to support the hypothesis that the ef fectiveness of oral contraceptives depends to some degree on postfertilizat ion effects. However, there are insufficient data to quantitate the relativ e contribution of postfertilization effects. Despite the lack of quantitati ve data, the principles of informed consent suggest that patients who may o bject to any postfertilization loss should be made aware of this informatio n so that they can give fully informed consent for the use of oral contrace ptives.