Highest among babies of mothers aged 40+
Notifications of congenital anomalies, 1989-2001
Between 1989 and 1994 the congenital anomalies notification rate for live births reported to the National Congenital Anomaly System (NCAS) in England and Wales had more than halved from 177 per 10,000 live births to 81 per 10,000 live births. This was due to the introduction of an exclusion list in 1990, with much of the decrease seen in those conditions that were on the exclusion list.
However, by 2001 the notification rate had increased to 114 per 10,000 live births. This was partly due to electronic transfer of data to NCAS from an increasing number of local registers from 1998 onwards, resulting in greater completeness and accuracy of the data.
The congenital anomaly notification rate for stillbirths fell from 656 per 10,000 stillbirths in 1990 to 461 per 10,000 stillbirths in 1992, increasing substantially to 970 per 10,000 stillbirths in 2001.
Between 1991 and 2001 the highest notification rates for total congenital anomalies were seen among mothers aged 40 years and over (145 per 10,000 births in 1991 compared with 152 per 10,000 in 2001). The second highest notification rates were among mothers aged under 20 years (113 per 10,000 births in 1991 compared with 125 per 10,000 births in 2001).
The notification rates for abdominal wall defects were highest for mothers aged under 20 years (8 per 10,000 births in 1991 compared with 9 per 10,000 in 2001). Notification rates for Down’s syndrome increased with an increase in maternal age ranging from 3 per 10,000 births for mothers aged 20 to 24 years; 13 per 10,000 for mothers aged 35 to 39 years and 38 per 10,000 for mothers aged 40 years and over.
In relation to birthweight, the highest notification rates were for babies weighing less than 2,000g at birth and lowest among babies weighing 3,500g and over.
Anomalies were more common in twins than in singletons. Between 1997 and 2000, notification rates for twins were 111 per 10,000 births compared with 102 per 10,000 for singletons.
Source: National Congenital Anomaly System (NCAS), Office for National Statistics ONS unpublished linked data
The purpose of the exclusion list was to advise notifiers of the conditions that should be notified in order to reduce the burden on those notifying and to improve reporting compliance.