In this prospective, case-control study, a step-wise logistic regression model was used to examine the relationship between the consumption of oral contraceptives before pregnancy and the potential increase in the risk of miscarriage. Consumption of oral contraceptives for more than 2 years before pregnancy is associated with a higher risk of miscarriage. In this prospective, case-control study, a step-wise logistic regression model was used to examine the relationship between the consumption of oral contraceptives before pregnancy and the potential increase in the risk of miscarriage. Consumption of oral contraceptives for more than 2 years before pregnancy is associated with a higher risk of miscarriage.