Objective Inconsistent outcome selection and reporting in clinical trials are important sources of research waste; it is not known how common this problem is in neonatal trials. Our objective was to determine whether large clinical trials involving infants receiving neonatal care report a consistent set of outcomes, how composite outcomes are used and whether parents or former patients were involved in outcome selection.

Design A literature search of CENTRAL, CINAHL, EMBASE and MEDLINE was conducted; randomised trials published between 1 July 2012 and 1 July 2017 and involving at least 100 infants in each arm were included. Outcomes and outcome measures were extracted and categorised by physiological system; reported former patient and parent involvement in outcome selection was extracted.

Results Seventy-six trials involving 43 126 infants were identified; 216 different outcomes with 889 different outcome measures were reported. Outcome reporting covered all physiological systems but was variable between individual trials: only 67/76 (88%) of trials reported survival and 639 outcome measures were only reported in a single trial. Thirty-three composite outcomes were used in 41 trials. No trials reported former patient or parent involvement in outcome selection.

Conclusions Inconsistent outcome reporting and a lack of parent and former patient involvement in outcome selection in neonatal clinical trials limits the ability of such trials to answer clinically meaningful questions. Developing and implementing a core outcome set for future neonatal trials, with input from all stakeholders, should address these issues.