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Objective To examine trends in incidence of hypoxic-ischaemic encephalopathy in term infants over a twenty-one year period.

Design A retrospective analysis of medical records of all term infants admitted to a neonatal unit with hypoxic-ischaemic encephalopathy during the years 1992–1996 (period C) and a comparison with data from the years 1976–1980 (period A) and 1984–1988 (period B) from the same unit (previously published1).

Setting A District Health Authority in Central England serving a population of about 450,000.

Sample All term infants admitted with clinical features of hypoxic-ischaemic encephalopathy.

Main outcome measures Incidence of three grades of hypoxic-ischaemic encephalopathy, disability and mortality.

Results In each five year period there were similar numbers of births. Over the time-span of this study the stillbirth rate and neonatal mortality rate has consistently fallen. The overall incidence of hypoxicischaemic encephalopathy in term infants was significantly lower (P < 0.001; OR 0.42 CI 0.29–0.59) in the present study period (C) compared with the earlier study period B (1.9 vs 4.6 per 1000 total live births). The fall in moderately and severely affected infants between the present and the first study period was significant (1.2 vs 2.6 per 1000 total live births, P < 0.001: OR 0.46 CI 0.29–0.72). The number of deaths and the incidence of cerebral palsy in survivors fell progressively over the 21 years spanned by this study.

Conclusion This study shows that the incidence of hypoxic-ischaemic encephalopathy and its sequelae in term infants has fallen significantly. The use of cardiotocography and caesarean section rates have risen but the relative contributions of changes in clinical practice are uncertain.