This study was undertaken to evaluate the effect of maternal intravenous (IV) administration of glucose on fetal breathing and its associated fetal heart patterns. Sixteen healthy women at term gestation participated in the study. The outcome of each of the pregnancies was normal. Fetal breathing and fetal electrocardiograms were simultaneously recorded by real time sonography and a fetal monitor respectively, and then digitized into a microcomputer. These women were studied for a 25-minute control period, given 50 gm of glucose IV and then, 20 minutes later, restudied for an additional 25-minute period. The results indicate that fetal breathing movements lasted for 24.8 +/- 6.2 percent of the time during the control period (mean +/- SEM) and were increased to 63.2 +/- 11.5 percent following the injection of glucose (P less than 0.01). Fetal heart rate decreased during fetal breathing by 2.3 and 2.1 beats per minute, before and after glucose administration, respectively (NS). Fetal breathing was associated with increased beat-to-beat variability by 1.32 +/- 0.5 and 1.27 +/- 0.3, before and after glucose administration, respectively (NS). This study confirms previous reports that the amount of time the fetus spends making breathing movements is significantly increased following maternal glucose administration, and demonstrates that the injection of glucose does not alter the modulation of fetal heart rate and beat-to-beat variability by fetal breathing
