[Maturity of lungs and bones at delivery. Comparison between surface tension measurement of the amniotic fluid and determination of size of infant knee-joint nuclei (author's transl)].

In 47 deliveries of term infants lung maturity studies (surface tension measurements in the Wilhelmy balance) were performed in the amniotic fluid collected at amniotomy. During the first three days post partum the bone age was assessed by radiological measurements of the epiphyseal centers. There was no correlation between the degree of lung- and scelettal maturity. These unexpected findings can be explained by 1) the biological variability in the degree of maturation of both organ systems 2) the false negative rate of both methods 3) the interesting fact, that those cases with spontaneous onset of contractions presented with a higher degree of lung maturity than those in whom labor was induced by amniotomy despite the fact that their pregnancies were of shorter duration. From the results of this study a certain link between the complete maturation of the lung and the spontaneous onset of uterine contractions might be assumed. With the concommitant use of both methods the false negative rate dropped to 1.2%. Consequently a radiological estimation of fetal bone age should be performed in case lung maturity studies are unequivocal.