Effects of maternal hyperoxia on the biophysical assessment of fetuses with suspected intrauterine growth retardation

Fifty-two third-trimester fetuses with suspected intrauterine growth retardation were studied by means of a computer-assisted biophysical assessment scheme, which used maternal hyperoxia as a diagnostic probe. Biophysical data examined included percentage of time spent in breathing, mean breath rate, and percentage of time spent in body movement during a 90-minute observation: 30-minute baseline, 15-minute hyperoxia, and 45-minute posthyperoxia. Mean baseline movement in fetuses found as neonates to have intrauterine growth retardation (N = 18) was significantly lower than that of normal fetuses (N = 34). Fetal body movements and breathing movements increased significantly after hyperoxia in the intrauterine growth retardation group but not in the normal group. Increases of more than 75% over baseline for fetal breathing and more than 250% over baseline for fetal body movements yielded a sensitivity of 56%, specificity of 94%, positive predicative value of 83%, and negative predicative value of 80%. Maternal hyperoxia during biophysical testing may improve the accuracy of detecting intrauterine growth retardation.