Neonatal nucleated red blood cell counts - Relationship to abnormal fetoplacental circulation detected by Doppler studies

Increased neonatal nucleated red blood cell counts are thought to be relate d to intrauterine hypoxemia. We sought to determine the effect of increasin g circulatory impairment in fetuses on the neonatal nucleated red blood cel l count. One hundred thirty-four singleton pregnancies were included in the study and were allocated to 4 study groups according to Doppler findings. The systolic-to-diastolic ratios of the umbilical artery, fetal aorta, midd le cerebral artery, and uterine arteries were recorded. Fetuses were assign ed to the following groups on the basis of the last Doppler examination bef ore delivery: group 1, normal systolic-to-diastolic ratios in the examined vessels; group 2, a systolic-to-diastolic ratio greater than 2 SD above the mean for gestational age in the umbilical artery or fetal aorta and no abn ormal Doppler findings in the uterine arteries; group 3, systolic-to-diasto lic ratios greater than 2 SD above the mean for gestational age in all exam ined vessels; and group 4 absence of end-diastolic velocity in the umbilica l artery or fetal aorta and systolic-to-diastolic ratios greater than 2 SD above the mean for gestational age in the uterine arteries. A blood sample from the umbilical artery was obtained within 1 minute after birth, and nuc leated red blood cells per 100 white blood cells were counted by light micr oscopy. Nucleated red blood cell counts were higher in fetuses in group 4 ( median, 72.0; range, 9-720; P < .001) and group 3 (median, 38.4; range, 7-2 01; P < .001) than in fetuses in group 1 (median, 5.1; range, 0-20). Neonat es in group 4 had significantly lower birth weights (P < .001), lower arter ial and venous pH values (P < .05), and lower Apgar scores after 5 minutes (P < .01) as well as an increased likelihood of cesarean delivery because o f fetal distress (P < .001). The number of fetuses in group 4 with a cord b lood base deficit of less than -8 mmol/L was increased. Nucleated red blood cell counts were comparable in fetuses in group 2 (median, 5.4; range, 0-3 7) and group 1. In groups 1 to 3 no brain-sparing effect occurred, whereas in 15 of 21 cases in group 4 a brain-sparing effect was present. Multivaria te analysis revealed that Doppler results of the umbilical artery, fetal ao rta, and uterine arteries were independent determinants of neonatal nucleat ed red blood cell count. Increasing abnormalities seen on fetoplacental Dop pler studies are associated with increasing numbers of nucleated red blood cells at birth. Given the known relationship between abnormal Doppler flow and intrauterine hypoxemia, the neonatal nucleated red blood cell count mig ht become an additional valuable tool in the surveillance of growth-restric ted fetuses.