The effect of failed appointments at a teratogen information service (TIS) clinic on pregnancy outcome is not known. The objectives of our study were 1) to identify predictors of failed appointments and 2) to evaluate if failed appointments were associated with a higher rate of adverse pregnancy outcome among women booked for counseling at a TIS clinic over 5 consecutive months. Of 242 patients scheduled to come to clinic, 154 were followed-up at 20 weeks gestational age. Women who were pregnant at 20 weeks were more likely to have attended the clinic (81% attendance rate), than women who had a spontaneous abortion, a therapeutic abortion, or an ectopic pregnancy (54% attendance rate) (P = 0.003). Independent predictors of failed appointments included exposure to illicit drugs, history of previous spontaneous abortion, and a main concern that was a nonmedication exposure. In conclusion, pregnant women who failed appointments at a TIS clinic are at greater risk for not being pregnant at 20 weeks gestational age than those who attended the clinic. Telephone counseling should be considered in selected cases to ensure that all women get relevant information at the time of appointment booking.