By means of the method of polimerase chain reaction the frequency of blank allele of genes GSTP1, GSTM1, and the frequency of polymorphous alleles of gene GSTP1 in 40 pairs with habitual noncarrying of pregnancy at early stages were studied. The results of the investigation testify to the high rate of gomozygotes GSTT1 0/0 in pairs with habitual noncarrying of pregnancy in comparison with indices in general population of North-West region of Russia (37,7% and 23,3% correspondingly).
 The genes GSTM1, GSTT1, GSTP1 code enzymes, which take part in the second phase of xenobiotic detoxication system. Taking into consideration that protein products of these genes to significant extent determine the effectiveness of 2nd phase of detoxication (neutralization of xenobiotics by glutathione binding), we are to suppose that unfavorable environmental factorsplay the important role in etiology and genesis of habitual noncarrying of pregnancy at early stages.