Nucleated red blood cells in cord blood of singleton term and post-term neonates

Objective: This study aims to determine if nucleated red blood cells are el evated in pregnancies that continue beyond 289 days of gestation. Study design: Cord blood was prospectively collected from term and post-ter m singleton gestations from August 1 to December 31, 1998. Umbilical artery nucleated red blood cells were counted per 100 white blood cells. The comp arison was made between pregnancies ending at 261-289 days (37.1-41.2 weeks ) of gestation and those ending after 289 days (greater than or equal to 41 .3 weeks) of gestation. Results: Cord blood from 304 cases was obtained and evaluated for nucleated red blood cells per 100 white blood cells. The mean value of nucleated red blood cells per 100 white blood cells in the post-term neonate group was s ignificantly higher than in the term neonate group (median 6.5, range 0-24 vs. median 3.7, range 0-14; p < 0.05). The values did not vary by fetal pre sentation, mode or duration of delivery. Neonatal outcome was comparable be tween both study groups. Conclusion: In post-term gestation after 289 days nucleated red blood cells in cord blood are significantly increased. These results point towards a d ifferent fetal oxygenation in post-term pregnancies beyond 289 days of gest ation and support the current practice of very close resting of fetal well- being under those circumstances.