Purpose Abnormal heart rate characteristics (HRC) of decreased variability and decelerations occur in preterm infants with sepsis and other pathologic conditions. We sought to determine whether an HRC index (HeRO score) in the first day after birth predicts death and morbidities and to compare it to an established risk index, the Score for Neonatal Acute Physiology (SNAP-II).

Methods The HRC index was analysed within 24 h of birth in 163 extremely low birth weight infants, and SNAP-II was calculated when data were available. Associations between the maximum HRC index (HRC-1), SNAP-II, and death and major morbidities were analysed using logistic regression to correct for gestational age.

Results HRC-1 was significantly associated with death, severe head ultrasound abnormalities (sHUS = grade 3–4 intraventricular haemorrhage or cystic periventricular leukomalacia), and late-onset septicemia (LOS) (Table). SNAP-II could be calculated in 122 cases (75%) and was correlated with HRC-1 (r = 0.50, p < 0.0001) and with death, sHUS, and bronchopulmonary dysplasia (BPD). Neither score predicted necrotizing enterocolitis or spontaneous intestinal perforation (NEC/SIP), or severe retinopathy of prematurity (ROP).

Conclusion The HRC index in the first day after birth predicts death and multiple morbidities in ELBW infants and is strongly correlated with SNAP-II, an established illness severity score.