Measurement, in amniotic fluid, of gamma-glutamyl-transferase (GGT) alkaline phosphatase and of thermostable and thermolabile (TLAP) isoenzyme allows to anticipate the unexpected risk of hyaline membrane disease. ROC method adapted to three ratio of these enzymatic activities shows that TLAP/GGT is the most performant at the level of 0.9 with a sensitivity of 96% and a specificity of 60%.