Background: The COVID-19 pandemic instigated multiple societal and healthcare interventions with potential to affect perinatal practice. We evaluated population-level changes in preterm and full-term admissions to neonatal units, care processes, and outcomes.Methods: We obtained information from the National Neonatal Research Database on all admissions to National Health Service neonatal units in England and Wales from 2012-2020. We evaluated admissions by gestational age, ethnicity, and Index of Multiple Deprivation, and key care processes and outcomes. We calculated the differences in numbers and rates between April-June 2020 (spring), the first three months of national lockdown and December 2019-February 2020 (winter), prior to introduction of mitigation measures (COVID period), and compared them with the corresponding differences in the seven previous years. We considered the COVID period highly unusual if the difference was smaller or larger than all previous corresponding differences, and calculated the level of confidence in this conclusion.Findings: Marked fluctuations occurred in all measures over the eight years with several highly unusual changes during the COVID period. Total admissions fell, having risen over all previous years (COVID difference: -1492; previous seven-year difference range: +100, +1617; pInterpretation: Our findings indicate substantial changes occurred in care pathways and clinical thresholds, with disproportionate effects on Black ethnic groups, during the immediate COVID-19 period, and raise the intriguing possibility that non-healthcare interventions may reduce extremely preterm births.Funding Information: Medical Research Council; Health Data Research UK.Declaration of Interests: NM reports grants outside the submitted work from the Medical Research Council, National Institute of Health Research, March of Dimes, British Heart Foundation, HCA International, Health Data Research UK, Shire Pharmaceuticals, Chiesi Pharmaceuticals, Prolacta Life Sciences, and Westminster Children’s Research Fund; NM is a member of the Nestle Scientific Advisory Board and accepts no personal remuneration for this role. NM reports travel and accommodation reimbursements from Chiesi, Nestle and Shire. All other authors report no declarations of interest.Ethics Approval Statement: The study was undertaken under approval from the Health Research Authority and Health and Care Research Wales, and with the agreement of all NHS neonatal units in England and Wales.