Intrauterine growth retardation in preterm infants ≤32 weeks of gestation is associated with low white blood cell counts.

It is unclear if very immature preterm infants who are born small for gestational age (SGA) have similar leukocyte counts as infants who are born appropriate for gestational age (AGA). Our study included 49 preterm infants with a gestational age ≤32 weeks and without exposure to chorioamnionitis and funisitis. Blood cells were counted in the first 2 hours of life. Eighteen SGA preterm infants were compared with 31 AGA preterm infants. Gestational age, sex, rate of caesarean section, and prenatal administration of corticosteroids did not differ between the groups. Median birth weight was 583 g in the SGA group versus 1100 g in the AGA group. Infants in the SGA group had significantly lower counts of leukocytes, total neutrophils, immature neutrophils, lymphocytes, and monocytes. These findings were not affected by maternal preeclampsia. No significant difference for nucleated red blood cell counts was found. Prenatal growth retardation is an independent factor for lower counts of different leukocytes in very immature preterm infants. It is not clear if these low leukocyte counts are associated with a higher risk of neonatal infections or if lower numbers of inflammatory cells protect the lung and brain of very immature SGA infants by reducing inflammatory events postnatally.