Fetal respiratory movements: relationship to postnatal respiratory capacity.

Sixty-six normal and 346 pathologic pregnancies have been investigated by means of dynamic ultrasound for determination of fetal intrauterine respiratory amplitudes in over 930 scans of 30-minute duration. Ten fetuses developed respiratory distress syndrome (RDS), and all of these showed antenatally either falling (more than 2 SD) or abnormally low thoracic and abdominal amplitudes. No fetuses with amplitude measurements within the normal range (mean +/- 2 SD) developed RDS (p less than 0.001, X2 test). In 74 women, measurement of amniotic lecithin was performed within one half hour before a dynamic ultrasound registration, predictive value, or specificity between these two methods in identifying RDS. The conclusion is that the pathogenesis of RDS may be both biochemical and biophysical, and that this new noninvasive method may easily be used as a screening test for postnatal respiratory capacity in high-risk pregnancies, since only 10 equal and regular respiratory movements are needed for this measurement.