Drugs contraindicated in pregnancy are medicines that should be avoided by pregnant women, since they carry a concern for teratogenicity or there is no indication for their use during pregnancy. It does not mean that exposures to these drugs always cause harm. The aim of the present study was to investigate the risk of adverse outcomes following maternal exposure to the drugs contraindicated in pregnancy. We retrospectively analyzed prenatal drug exposure records of the pregnant patients referred to the clinical pharmacology consultation service in a tertiary-level university hospital from January 2007 until December 2012. Exposures to category X drugs (CXD) contraindicated in pregnancy were evaluated. After the expected date of delivery, we collected data about pregnancy complications and the outcomes. For comparison the women in the exposed group (N=52) were matched with a control group (N=162) of pregnant women without teratogenic exposure. We observed only one baby born with a birth defect (congenital cryptorchidism) in CXD group (2.6%) and four in control group (RR 0.91; 95% CI 0.10- 7.94). The rates of adverse pregnancy outcomes including miscarriage, preterm birth and congenital abnormality were not significantly different from controls. However, the rate of elective termination of pregnancy was higher in women exposed to CXD while pregnant (RR 2.54; 95% CI 1.11- 5.80, p = 0.027). Contraceptive failure and unintended pregnancy are the reasons for inadvertent drug exposure and choosing abortion. The high perception of teratogenic risk among pregnant women may cause terminations of pregnancies. Individual risk assessment and avoiding the phrase `CXD` or `contraindicated in pregnancy` in counseling may help to reduce maternal concerns about medication use in pregnancy.

Keywords: contraindications; medication; newborn; birth outcome