Demographic characteristics, features of pregnancy and drug use patterns were compared across 132 Toronto-area (Canada) women contacting the Motherisk Alcohol and Substance Abuse Helpline at the Hospital for Sick Children who reported using ecstasy. 122 controls reporting no ecstasy use were selected from among women visiting the same clinic for more detailed counseling within the same week as one ecstasy-using respondents. Of the 132 ecstasy using respondents, 129 reported at least 1 ecstasy use during pregnancy. Of those 129, all 101 who chose to respond indicated discontinuation of ecstasy use during pregnancy (it is possible that at least some non -responders continued using ecstasy during pregnancy. Pregnant women reporting ecstasy use tended to be younger than controls (23.16 ± 4.6 for ecstasy group versus 31.18 ± 5.07 for controls) and tended to be white (number of white v. non-white respondents similar, 60 ecstasy users v 61 controls, but more controls reported belonging to all other non-white ethnicities listed.) Ecstasy users were more likely to have unplanned pregnancies (5/32 versus 32/78), and they were more likely to have had therapeutic, but not spontaneous, abortions. Ecstasy users drank more heavily than controls (17/59 v. 1/29) and were more likely to drink moderately or heavily during pregnancy (46/105, 21 moderate, 25 heavy for ecstasy users, for controls 12 /118, with 11 moderate, 1 heavy). Ecstasy users had tried a greater number of drugs than had controls (for instance, ketamine, amphetamine, GHB, magic mushrooms). Because of low drug use rates in controls, it is hard to compare rates of drug discontinuation after pregnancy for other drugs, but it appears that not all ecstasy users reporting use of marijuana, cocaine or amphetamine discontinued use after pregnancy (23/32 reported discontinuation of cocaine, and 12/15 reported discontinuing amphetamine use in pregnancy. It is interesting to compare the adverse effects after ecstasy use reported by this sample with those reported elsewhere (e.g. Vollenweider et al. 1998; Solowij et al. 1992), with vomiting the most commonly reported adverse effect (18/78, with 34/78 reporting the presence of any adverse effects). Sweating (3/34) and depression 3/34) the next most commonly reported adverse effects. When Liechti and colleagues investigated gender differences in subjective effects and side effects reported in clinical trials with MDMA (Liechti and Vollenweider, 2001), men, and not women, were more likely to report sweating and nausea. The authors conclude that investigating the potential teratogenic effects of ecstasy/MDMA are made difficult by the fact that many users are polydrug users, so that any effects observed cannot be easily attributed to ecstasy use alone. The authors also note that ecstasy-induced hyperthermia may itself be teratogenic.