The Office for National Statistics runs the National Congenital Anomaly System. Congenital anomalies are voluntarily notified by health authorities. Data on anomalies are available for a number of variables including by mother's age, month of birth, sex, birthweight, and multiplicity.

Data cover England and Wales and are available at health authority and postcode level.

The data are published annually by the end of the year following the reference year.

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