Transcervical chorionic villus sampling with ultrasound guidance at the 11-th week of pregnancy was made at a woman with the history of one lethal case of Sandhoff disease. The total hexosaminidase and the hexosaminidase A were determined. At the 16-th week amniocentesis was performed and the characteristic enzymes were determined from the amniotic cell culture. The results of the examinations made possible to advise the patient to carry out the pregnancy. The examinations after delivery confirmed the newborn to be a carrier.