Relationship between amylase concentration, L/S ratio and lecithin concentrations in amniotic fluid

Amylase concentration, L/S ratio and lecithin concentration were measured in 110 samples of amniotic fluid in 106 uneventful pregnancies. Amylase concentrations lower than 200 U/l corresponded significantly (p less than 0.001) to a gestational age less than the 37th week as well as to a L/S ratio lower than 2 and to lecithin concentrations lower than 3.5 mg%. Furthermore, amylase values higher than 300 U/l corresponded significantly (p less than 0.001) to a gestational age over the 37th week as to an L/S ratio over 2 and to lecithin concentrations over 3.5 mg%. On the other hand amylase concentrations ranging between 200 and 300 U/l failed to show any significant relationship neither to the age of gestation nor to the concentration of phospholipids. These findings show that the amylase test is a useful method for prediction of fetal maturity. Since the procedure of determination of the amylase concentration is very simple, cheap and rapid, the test can be used as screening method. However, when amylase concentrations are found to range between 200 and 300 U/l specific tests for assessment of fetal maturity have to be applied.