Objective: We attempted to determine, in a pilot study, whether recombinant human granulocyte colony-stimulating factor, administered to women with an imminent delivery at < or = 30 weeks' estimated gestational age, crosses to the fetal circulation and stimulates fetal neutrophil production.
Study design: We measured granulocyte colony-stimulating factor and neutrophil concentrations in the blood of the mothers and in the umbilical venous cord blood after a single intravenous dose (25 micrograms/kg) of recombinant granulocyte colony-stimulating factor given to 11 women in whom preterm delivery was imminent and compared these with values from 34 control women and 35 cord sera.
Results: Ten infants were delivered within 30 hours (10.8 +/- 8.9, mean +/- SD) of the granulocyte colony-stimulating factor administration ("early delivery"), and two were delivered after 54 and 108 hours, respectively. In the early delivery group maternal granulocyte colony-stimulating factor concentrations and blood neutrophil levels were higher than in controls. However, no difference was seen in the cord blood neutrophil concentrations. In the late delivery group, although maternal serum and cord blood granulocyte colony-stimulating factor concentrations did not differ from controls, cord blood neutrophil levels were higher (25,900 and 17,700 cells/microliters) than controls (3500 +/- 2000 cells/microliters, p < 0.05) and remained elevated for 1 week. Specifically, the blood neutrophil levels on days 5 and 8 were 12,000 and 17,000, respectively, for these patients, whereas the reference range upper limit for controls was 6000 cells/microliters.
Conclusion: Administration of recombinant granulocyte colony-stimulating factor to pregnant women with an imminent preterm delivery may result in the transplacental passage of a measurable quantity of granulocyte colony-stimulating factor, an amount that can have a biologic effect on the fetus. These events were most noticeable in those patients who received granulocyte colony-stimulating factor at least 30 hours before being delivered of their infants.