Little information exists on the possible teratogenic effect of modern antiobesity drugs. The present study refers to orlistat, sibutramine, and rimonabant. Data in the Swedish Medical Birth Register were utilised. During the years 1998–2011, among 392,126 infants born, 509 had been exposed to antiobesity drugs in early pregnancy: 248 to orlistat, 242 to sibutramine, 12 to rimonabant, 13 to unspecified antiobesity drugs. Simultaneous use of orlistat and sibutramine occurred in six cases. No increase in major malformation risk was seen after orlistat (relative risk=0.42, 95% confidence interval 0.11–1.07) but a significantly high risk was seen after sibutramine (relative risk=1.81, 95% confidence interval 1.02–2.99). The latter effect, which seemed to be mainly due to an increased risk for a cardiovascular defects, may be related to the capacity of the drug to prolong QT-time. Sibutramine has been withdrawn in Europe but is still available on the Internet and is a component in some slimming preparations. Among the 12 infants exposed to rimonabant, two which were in a twin pair were malformed.