Nucleated red blood cell count and doppler ultrasound in low- and high-risk pregnancies

The aim of this study was to evaluate the influence of circulatory deterioration in small-for-gestational-age fetuses (SGA) on the nucleated red blood cell count (NRBC).

During a 12-month period 194 patients with a complete NRBC count post-partum were enrolled in the study. Using pulsed wave colour Doppler ultrasound we recorded blood flow velocity waveforms from both uterine arteries and from the umbilical artery and/or from the fetal aorta. Patients were assigned to seven groups according to the results of the Doppler examination. Mean outcome measures were birthweight, gestational age at delivery, NRBC count, incidence of preeclampsia or SGA and need of neonatal intensive care.

Significantly higher nucleated red blood cell counts than in all other groups were found in cases with abnormal Doppler findings in both uterine arteries and the umbilical artery and/or fetal aorta (p<0.001). These newborns had significantly lower birth weights (p<0.01, p<0.001), lower gestational age (p<0.001), an increased likelihood of caesarean section for clinical signs of fetal distress (p<0.001) and had to be transfered more frequently to the neonatal intensive care unit (p<0.01, p<0.001).

Patients with abnormal Doppler velocimetry waveforms of the uterine arteries in the presence of an abnormal umbilical artery or fetal aorta Doppler findings have a high risk of prematurity, preeclampsia or delivering a small-for-gestational-age newborn. Fetal response to uteroplacental insufficiency may lead to elevated nucleated red blood cells in the fetal blood. This fact might help to discriminate the small-for-gestational-age fetus who is growth-retarded and suffers from chronic placental insufficiency from the small but healthy fetus.