Objective To determine placental characteristics associated with neonatal encephalopathy (NE) and correlate these with short- and long-term neurodevelopmental outcome.

Design Case/control study.

Setting Neonatal Intensive Care Unit, Rotunda Hospital, Dublin, Ireland.

Patients Newborns ≥36 weeks gestation, with NE (cases). Healthy term newborns (controls).

Interventions Placental pathology was obtained from the official placental report. Brain MRI was blindly reviewed. Children were assessed using a variety of standardised assessments. Data were analysed using multinomial logistic regression analysis.

Main outcome measures RRR for grade of encephalopathy. OR for neurodevelopmental outcome.

Results Placental reports were available on 141 cases (76 grade 1; 46 grade 2; 19 grade 3) and 309 control infants. Meconium phagocytosis, haemorrhage, raised placental to birth weight ratio and/or markers of infection/inflammation were independently associated with NE and showed a synergistic effect, when combined, for short- and long-term impairments.

Conclusions Evaluation of the mechanisms leading to the placental characteristics identified may help to characterise the causal pathway of NE.