[Ultrasound diagnosis of fetal lung maturity]

Until now, it has been possible to determine fetal pulmonary maturity only by amniocentesis. Since the functional changes of the fetal lung leading to maturity are also morphologically apparent, pulmonary maturity can be demonstrated sonographically. Obtaining a uniform value for maturity is a problem, since the position of the fetus, the mother's constitution and the instrument setting all influence assessment. The fetal liver was therefore used as a reference organ, since it is subject to the same influences. By frequency analysis of both organs and calculation of the ratio between the frequencies obtained, a mathematical value can be calculated by which pregnancies can be compared and which, as our studies showed, represents a measure of pulmonary maturity. This was documented in 348 patients. It was shown by amniocentesis in 32 patients and the postpartal condition of 25 premature births that a value of 1.11 for this ratio between lung and liver represents the borderline between pulmonary immaturity and maturity. Lower values indicate maturity. If these results are confirmed by further studies on larger groups of patients, it will in future be possible to determine fetal pulmonary maturity very easily and non-invasively.