Amniotic fluid isoamylase activity in uneventful pregnancies

A kinetic test (Phadebas) was used to determine the isoamylase activity in 50 serum specimens and 159 samples of amniotic fluid. A highly significant difference between the isoamylase patterns of serum and amniotic fluid was ascertained which strongly supports the view that amylase activity in amniotic fluid is not of maternal origin. During the whole course of gestation the activity of pancreatic isoamylase was constantly low whereas there was an increase of nonpancreatic activity (S-type amylase) from 44 +/- 10 U/l in the 18th week of gestation to 445 +/- 170 U/l in week 39/40. A comparison between the dispersion of the ascertained values and the lecithin-sphingomyelin (L/S) ratio showed a clear overlapping. There was a correlation coefficient of r = 0.645 for 115 amniotic fluid specimens examined in our investigation. The findings show that the estimation of nonpancreatic isoamylase (S-type amylase) activity in amniotic fluid is a valuable indirect parameter for determining fetal maturity and fetal lung maturity. The easy and quick determination method will provide even those hospitals with an index of fetal maturity which are presently not in a position to estimate the L/S ratio, thus being of great assistance in the field of premature deliveries.