Objective To explore the association between concentrations of endogenous erythropoietin (EPO) in blood the first 2 weeks of life and neonatal disorders in extremely low gestational age newborns (ELGANs).

Design Prospective cohort study.

Setting Neonatal care units at 14 participating hospitals in the USA.

Patients 867 children born before the 28th week of gestation from the ELGAN study cohort.

Main outcome measures EPO blood concentrations were measured on postnatal days 1, 7 and 14. The following neonatal characteristics and disorders were registered: blood gases, early and late respiratory dysfunction, pulmonary deterioration, retinopathy of prematurity (ROP), necrotising enterocolitis (NEC) and bronchopulmonary dysplasia (BPD). We calculated the gestational age-adjusted ORs for having each disorder associated with an EPO blood concentration in the highest or lowest quartile, compared with infants whose EPO concentration was in the middle two quartiles on the corresponding day.

Results Newborns whose day-1 EPO was in the highest quartile were at increased risk for early and persistent respiratory dysfunction during the first 2 weeks of life, and NEC requiring surgery. The lowest EPO quartile on day 1 was associated with a decreased risk of moderate BPD. The association between low EPO and decreased risk of respiratory complications persisted on day 7. On day 14, being in the highest EPO quartile was associated with increased risk of ROP, and BPD not requiring ventilation assistance.

Conclusions EPO blood concentrations in extremely preterm newborns during the first 2 weeks of life convey information about increased risks of bowel, lung and retinal diseases.