Fetal breathing patterns in intrauterine growth retardation.

Fetal breathing movements were studied with real time ultrasound in 21 normal fetuses and 30 fetuses born small-for-dates (less than the 5th centile). The events of the study period were recorded on punched paper tape which was subjected to computer analysis. In the normal group the percentage time of breathing was 54 +/- 12.7 (mean +/- SD). The breath to breath interval was 1.34 +/- 0.25 seconds and the coefficient of variation of this interval was 49.6 +/- 7.7 per cent. In 17 of the small-for-dates group amount of breathing was reduced with short breathing episodes and long apnoea intervals. In the other 13 patients in the small-for-dates group the coefficient of variation for the breath to breath interval was significantly reduced (39.6 +/- 7.9 per cent, p less than 0.01).