Determination of fetal maturity and of development of the fetal lungs by means of combined methods.

The validity of the assessment of the fetal age and pulmonary maturity was evaluated on 369 patients at various stages of normal pregnancy and complicated by diabetes, toxemia and fetal anencephaly. Gestational maturity was assessed by ultrasonic measurement of the fetal biparietal diameter and by analysing constituents of amniotic fluid (creatinine, bilirubin, fat cells) while pulmonary maturity was assessed from the L/S ratio in the amniotic fluid. Each individual method has a wide margin of error, however, ultrasound cephalometry gave the best prediction for determination of fetal age. In 135 selected cases lung maturity was assessed by using two techniques, a thin layer chromatographic determination of the lecithin/sphingomyelin ratio in the amniotic fluid and a rapid semiquantitative test to determine the titre of surfactant which generates stable foam in presence of ethanol. The results obtained by the two methods correlated well and were reliable in predicting the respiratory distress syndrome. It appears that these methods make it possible to obtain greater margins of reliability. The role of fetal and maternal factors in the maturation of fetal lungs was also studied in several pathological conditions and it was noted that in many cases of maternal diabetes mellitus lung maturity was reached at a later age than in normal pregnancies. It is condluded that if termination of pregnancy is indicated, the physician should rely more on the assessment of lung maturity than on indicators of gestational age.