Fetal respiratory movements: a nomogram for fetal thoracic and abdominal respiratory movements.

A nomogram for fetal thoracic and abdominal amplitudes during respiration is presented. The correlation coefficient between the thoracic amplitude and gestational age was 0.973, and that for the abdominal amplitude was 0.920, thus suggesting a strong correlation between gestational age and respiratory amplitude (p less than 0.001), whereas no correlation was found between respiratory amplitude and fetal weight. The respiratory amplitudes were not influenced by intake of meals or time of the day when examination was carried out. The respiratory amplitudes were found to be very reproducible (SEM=0.1 mm, N=42). This new noninvasive method to predict the respiratory distress syndrome seems to be very promising.