Tribenoside is used for the treatment of haemorrhoids and varicose veins, frequently in pregnant women as well, but published data regarding its possible teratogenic effect are not available. Thus the risk of congenital abnormalities (CAs) was estimated in cases of pregnant women with oral tribenoside treatment (TT) in the Hungarian Case-Control Surveillance System of Congenital Abnormalities. Of 22,843 cases with CA, 174 (0.76%), while of 38,151 matched controls without CA, 285 (0.75%) were born to mothers with TT. There was no higher risk for total CAs after TT during any time of pregnancy but congenital hydrocephaly had a higher risk after medically recorded TT in the second and/or third month of pregnancy, i.e. critical period of this CA. In conclusion TT in pregnant women associated with a higher risk of congenital hydrocephalus in their children, however, this finding is based on only 4 cases therefore requires further confirmation in future studies.