Two parameters have been used to estimate the foetal pulmonary maturity: Clements' test or bubble test and palmitic acid/stearic acid ration. The reliability and the limits of these tests have been studied in function of several pathological pregnancies and the gestations's age. A value greater than 5 for the P/S ratio was a good pronostic at any gestational age. A value lesser than 5 should be examined according to this gestational age. A negative Clements' test has to be confirmed by an another amniocentesis, while a positive test have been followed always by a mature newborn's birth.