INFORMATION IN PRACTICE

Congenital anomaly surveillance in England--ascertainment deficiencies in the national system

¹ National Perinatal Epidemiology Unit, University of Oxford, Oxford OX3 7LF
² London School of Hygiene and Tropical Medicine, London WC1E 7HT
³ Faculty of Life and Health Sciences, University of Ulster, Newtonabbey, Co Antrim, BT37 0QB
⁴ Office for National Statistics, London SW1V 2QQ
⁵ North Thames Perinatal Public Health Unit, Northwick Park Hospital, Harrow, HA1 3UJ
⁶ School of Population and Health Sciences, Faculty of Medicine, University of Newcastle, Newcastle NE2 4HH
⁷ International Agency for Research on Cancer, 150, Cours Albert Thomas, 69372 Lyons, Cedex 08, France
⁸ Wessex Clinical Genetics Service, Princess Anne Hospital, Southampton SO16 5YA

Objective Firstly, to assess the completeness of ascertainment in the National Congenital Anomaly System (NCAS), the basis for congenital anomaly surveillance in England and Wales, and its variation by defect, geographical area, and socioeconomic deprivation. Secondly, to assess the impact of the lack of data on pregnancies terminated because of fetal anomaly.

Design Comparison of the NCAS with four local congenital anomaly registers in England.

Setting Four regions in England covering some 109 000 annual births.

Participants Cases of congenital anomalies registered in the NCAS (live births and stillbirths) and independently registered in the four local registers (live births, stillbirths, fetal losses from 20 weeks' gestation, and pregnancies terminated after prenatal diagnosis of fetal anomaly).

Main outcome measure The ratio of cases identified by the national register to those in local registry files, calculated for different specified anomalies, for whole registry areas, and for hospital catchment areas within registry boundaries.

Results Ascertainment by the NCAS (compared with data from local registers, from which terminations of pregnancy were removed) was 40% (34% for chromosomal anomalies and 42% for non-chromosomal anomalies) and varied markedly by defect, by local register, and by hospital catchment area, but not by area deprivation. When terminations of pregnancy were included in the register data, ascertainment by NCAS was 27% (19% for chromosomal anomalies and 31% for non-chromosomal anomalies), and the geographical variation was of a similar magnitude.

Conclusion The surveillance of congenital anomalies in England is currently inadequate because ascertainment to the national register is low and non-uniform and because no data exist on termination of pregnancy resulting from prenatal diagnosis of fetal anomaly.