Decrease in gamma-glutamyl transpeptidase activity in early amniotic fluid in fetal trisomy 18 syndrome.

A study was carried out in which activity of gamma-glutamyl transpeptidase was measured in 259 samples of amniotic fluid obtained at various weeks of pregnancy. Two hundred and twenty-eight of the babies subsequently delivered had no chromosome abnormality and served as controls, while in 31 various chromosome abnormalities were detected. Mean activity of gamma-glutamyl transpeptidase in the control samples at 15 weeks was 602 U/l. Activity in the samples obtained in cases of fetal chromosome abnormality was generally below this: it was below the 10th percentile in 74% of the samples and below the 2.5th percentile in 52% of the cases. It is concluded that assay of gamma-glutamyl transpeptidase activity is a rapid preliminary test for prenatal diagnosis of chromosomal abnormalities.