In order to determine the effect of maternal fasting on human fetal breathing movements (FBM), 63 healthy pregnant women with singleton uncomplicated pregnancies of 30 weeks' gestation or more, and who were fasting during Ramadan, were recruited. Maternal blood glucose level and fetal movements were recorded during and after fasting. Statistical comparison of samples before and after a meal was made using Wilcoxon's signed-ranks test. Maternal glucose level during fasting (5.1 +/- 0.5 mmol/l) was significantly (P = 0.01) lower than after breakfast (5.3 +/- 1.0 mmol/l). There was a significant association between maternal glucose levels and numbers of days faster (P = 0.01). The time needed to detect breathing movements was significantly longer (P = 0.005) during fasting than postprandial. The continuous variety of fetal breathing movement was significantly (P = 0.02) less during fasting compared to postprandial. It is concluded that intermittent maternal fasting is associated with a significant alteration in the frequency and pattern of human FBM.