Objective To assess the association between a patent ductus arteriosus (PDA) on day 3 of life and severe morbidity and mortality.

Design Cohort study.

Setting Neonatal Intensive Care Unit, Aarhus University Hospital, Denmark.

Patients All neonates with a gestational age less than 32 weeks admitted from 2010 to 2012.

Interventions All neonates (n=183) were routinely screened with echocardiography for PDA on day 3 of life. Information on baseline characteristics and outcome was collected by structured coding sheets and medical records.

Main outcome measures The association among PDA diameter and pulmonary haemorrhage, intraventricular haemorrhage (IVH), necrotising enterocolitis, bronchopulmonary dysplasia (BPD), death, and the composite outcome of death or severe morbidity was assessed.

Results In neonates, born prior to 28 gestational weeks, a PDA on day 3 of life was associated with a threefold increase in odds of death or severe morbidity compared with neonates without PDA (OR=3.4; CI 1.1 to 11). The odds were highest in neonates with a large PDA (diameter ≥1.5 mm). Neonates with a large PDA were also found to have increased odds of IVH (OR 4.2; CI 1.3 to 14) and BPD (OR 3.7; CI 1.0 to 14) compared with neonates with no PDA.

Conclusions In neonates born with a gestational age below 28 weeks the presence of a PDA on day 3 of life was associated with adverse outcome; this association was even more pronounced with a large PDA. Thus, early echocardiography may facilitate the identification of neonates suitable for a targeted approach to intervention in future randomised controlled trials.