Neonatal reticulocytes among preterm infants of small for gestational age

We previously reported that higher reticulocyte counts were observed in earlier preterm infants. Here we present an additional study that focused on reticulocyte counts among preterm infants of small for gestational age (SGA). To assess the relationship between SGA and perinatal variables during the early postnatal period.

A single-center study was undertaken at Ohta Nishinouchi Hospital between April 1, 2016 and June 30, 2021, using blood samples prospectively collected from infants admitted to the neonatal intensive care unit. These were assessed by univariate analysis and multivariate logistic regression analysis.

A total of 467 preterm infants were analyzed, 367 (78.6%) non-SGA and 100 (21.4%) SGA. The median [interquartile range (IQR)] GA (weeks) for the two groups was 33 (31-35) and 34 (31-36), respectively (p = 0.058). The median (IQR) BW (g) for the two groups was 1888 (1480 to 2195) and 1381 (1019 to 1782), respectively (p < 0.001). There were significant relationships between SGA and BW (p < 0.001, OR, 0.997; 95% CI, 0.996 to 0.998), umbilical artery pH (p = 0.038, OR, 0.031; 95% CI, 0.010 to 0.827), Apgar at 5 min (p < 0.001, OR, 1.816; 95% CI, 1.301 to 2.536), nucleated erythrocyte count (p = 0.027, OR, 1.013; 95% CI, 1.001 to 1.024), reticulocyte count (p < 0.001, OR, 0.992; 95% CI, 0.988 to 0.995) and chorioamnionitis (p = 0.019, OR, 0.427; 95% CI, 0.210 to 0.868).

These results suggest that preterm infants with SGA adapted more rapidly to the postnatal environment than did non-SGA preterm infants. Moreover, a lower reticulocyte count among preterm infants born SGA may be an indicator of good adaptation to the extra-uterine environment during the early postnatal period.