From 1 April 2015 we are part of Public Health England

We are still maintaining this website until further notice.

Anomaly Data

Regional data: geographical anomaly data based on postcode of pregnancy is provided for the South West region. All anomalies and births for southern Wiltshire have been removed from this dataset until the notifications from this area can be considered representative for the entire reporting period; work is in progress to reach this goal.

Regional data is available to everyone as rates and percentages (see "South West Region data for public access" below).

Trust data: anomaly data at the level of individual NHS trusts is available to approved trust staff at the trusts for which representative data is currently available. This is based on booking hospital, and as such it will include some cases with postcodes outside our boundaries. It is anticipated that Salisbury NHS Foundation Trust will be publishable in the near future. Please contact SWCAR to request a copy of your trust’s dataset; please note you will need a valid NHSmail address to receive this data.

Anomaly group data last updated: May 2015.

South West region and trust anomaly data for the years 2003 - 2013 is included in the tables below.

More information about the data and status of anomalies

South West Region data for public access

South West Region cases by anomaly group

South West Region cases by maternal age

South West Region cases by birth outcome - contact SWCAR to get access to this dataset

South West Region cases by when anomaly first suspected

South West Region and hospital data for authorised persons

Please contact SWCAR to get access to these datasets. You will need a valid NHSmail address to receive this data.

Data and the status of anomalies

Up to data links

Anomaly Groups

Only confirmed and probable anomalies are included in the data. Anomalies are grouped according to body system for the purposes of data presentation. Particular conditions in each group are also presented individually as a sub-group, being either more common or of clinical interest. Cases with multiple anomalies within the same anomaly group or sub-group, are counted only once in that group or sub-group. For example, a baby with transposition of the great vessels and a VSD will be counted once in each of the ‘transposition great vessels’ and ‘VSD’ minor sub-groups, once in each of the ‘All complex cyanotic CHD’ and ‘All septal defects’ sub-groups, but only once in the ‘Circulatory’ group.


Rates are crude rates per 10,000 registered births (live births and still births) unless otherwise stated. The numerator includes cases with all outcomes (live birth, stillbirth, termination of pregnancy and spontaneous fetal loss) but the denominator includes only registered births.

For the regional data, live birth prevalence rates are also presented. These include only cases ending in live birth in the numerator, and similarly the regional live birth data provide the denominator.

The birth data used as denominator data when calculating regional prevalence rates are based on Office for National Statistics (ONS) published data for live births and stillbirths, and are adjusted for the ascertainment concerns in southern Wiltshire mentioned above. Trust birth data are obtained from hospital staff and are used for calculating prevalence rates for individual trusts.

Reliable sources have not yet been established for rates of termination, termination for fetal anomaly and spontaneous fetal loss. These will be required for publication of more detailed anomaly rates in the future. Alternative sources are being investigated.

Allocation of anomalies and cases to data years

Data are assigned to a year on the basis of the date end of pregnancy (DEP), or the year end of pregnancy (YEP) where the precise date in that year is not known. If neither DEP nor YEP is known the expected date of delivery (EDD) is used.

Regional data

Presently the SWCAR region boundary is defined by 11 Clinical Commissioning Groups (CCGs). These are Gloucestershire (11M), South Gloucestershire (12A), Wiltshire (99N), Swindon (12D), Bristol (11H), North Somerset (11T), Bath and Northeast Somerset (11E), Somerset (11X), North, East and West Devon (99P), South Devon and Torbay (99Q) and Kernow (11N).

A neighbouring anomaly register, the Wessex Antenatally Detected Anomalies Register (WANDA), also historically covered the southern Wiltshire area around Salisbury District Hospital, which has led to incomplete ascertainment for this area on the SWCAR database. The SWCAR regional data are therefore currently adjusted to remove this sub-regional area from both the numerator and denominator so that the published prevalence rates are more representative. Work is in progress to resolve this under-ascertainment, primarily historical, to be able to report more complete anomaly data that remains representative.

SWCAR regional datasets are therefore population-based. Only cases with relevant postcodes, which identify the NHS geography codes to determine resident status, are included in the data. Presently, postcode during pregnancy is used to define case inclusion wherever possible.

Trust data

Data is also available by NHS trust as well as for the region. Cases are assigned according to the hospital where the pregnancy was booked, rather than where delivery occurred. Thus a pregnancy booked at hospital A but referred to hospital B for delivery, will be included with the dataset for the trust responsible for maternity services at hospital A.

High-risk pregnancies, including those where serious congenital anomalies are detected antenatally, are normally referred to a tertiary centre for on-going management. This typically results in the tertiary hospital delivering more babies with anomalies than reflects the prevalence amongst its local resident population, and similarly the referring hospital delivering less. The presentation of data according to booking hospital therefore reflects the responsible NHS trust’s local resident population.

Coding of anomalies

Anomalies are coded using the World Health Organisation’s International Statistical Classification of Diseases and Related Health Problems ICD-10. Where possible SWCAR codes to a greater level of detail than appears in ICD-10 by using the Paediatric Adaptation for the Q-chapter of congenital anomaly codes, which was developed by the Royal College of Paediatrics and Child Health in 2002. For further information on ICD-10 see the ICD-10 Version:2010 website.

Status of anomalies

Reported anomalies are given a confirmation status depending on how much detail has been provided and on the reliability of the source. Each anomaly is classed as confirmed, probable or suspected.

Confirmed anomalies

We have details of the test confirming the anomaly or we consider the source to be sufficiently reliable. We confirm some anomalies antenatally when reported by fetal medicine specialists, such as anencephaly and renal agenesis.

Probable anomalies

We consider these anomalies to be likely but do not have full diagnosis details. Most of these anomalies have been reported by IT departments. We try to obtain follow up details to confirm anomalies reported in this way.

Suspected anomalies

Anomalies remain suspected when they are reported antenatally but we receive no follow up at birth. Some conditions reported by IT departments or notified with insufficient details will remain suspected until further confirmation is obtained.

Notes on particular anomalies:

Hydronephrosis (dilated renal pelves)
These cases are only confirmed if the condition persists postnatally, verified by renal ultrasound. They are only included in the renal anomaly data if the measurements are 10mm or over at any time. Where the dilatation is mild (5-9mm) the data is collected by SWCAR but reported on separately, see below.

Undescended testes
Not included in genital anomaly group. Large numbers reported and the register is unable to follow up cases to verify whether the problem persists or resolves.

This uro-genital anomaly is classified in SWCAR data as a Genital anomaly from 2007 (previously under Urinary)

Exclusion list

PDF file: SWCAR exclusion list

The European Register EUROCAT introduced an extended exclusion list in January 2005. This has been adopted by SWCAR for all data publication since 2007.

The minor anomalies on this exclusion list are NOT added to the database if they are the ONLY anomaly reported for a case. They are only recorded if they occur in association with other anomalies. This practice is in line with other UK registers.

SWCAR therefore records ALL anomalies reported per case. For syndromes this means dysmorphic features are recorded along with the primary diagnosis and any major anomalies (i.e. those that do not appear on the exclusion list and would be recorded even where they occurred in isolation). However, only the major anomalies appear in the data presented on the website; the minor anomalies are not included in the counts or rates presented here but remain available for other purposes such as research.

Such cases will appear in each anomaly group where a major anomaly is coded: O: Genetic / multi-site disorders; E: Digestive if a cleft lip is reported; C: Circulatory if a heart anomaly is reported; but no case is counted more than once in any single anomaly grouping.

For our own purposes SWCAR has continued to collect and publish the following anomalies on the EUROCAT exclusion list:

The anomaly counts and rates for these anomalies are provided separately at the bottom of each table. These anomalies are still excluded from the totals for each table given in the first line ‘All cases’.

Conditions known to be secondary to another anomaly are not included in the counts/rates. Examples include: Pulmonary hypoplasia secondary to renal anomalies; PDA in ductus-dependant cardiac cases; PDA or other complication of prematurity.

Termination for Fetal Anomaly

Where a pregnancy is terminated following the identification of fetal anomaly, SWCAR aims to obtain post mortem confirmation of the notified anomalies. However, this is not always possible as consent for post mortem may not be given and problems can arise with service provision. Confirming all anomalies risks over-reporting, while simply recording them all as suspected risks under-reporting. The approach taken is to confirm anomalies that have been demonstrated through clinical practice to be diagnosed reliably using appropriate antenatal testing, balanced with a consideration of the specialism of the reporting health professional, along with their own confidence in the diagnosis. In some cases a general anomaly code is allocated where it is clear that an anomaly is present but a specific diagnosis is not possible.

Case Ascertainment

SWCAR receives notifications of congenital anomalies from multiple sources: antenatal clinics, fetal medicine units, maternity units, neonatal units, paediatric departments, physiotherapy departments, clinical genetics departments, cytogenetics, and hospital inpatient data from IT departments.

Complete ascertainment is difficult to achieve and relies on workable reporting methods, the hard work of reporting health professionals around the region, and responding to changes in hospital systems and staff as effectively as possible. However, there is scope for fluctuations in reporting to lead to minor fluctuations in the data, although every effort is made to minimise this. Follow up is sought wherever possible and SWCAR seeks to establish new reporting sources, especially in the post-neonatal period to overcome under-notification of conditions diagnosed at a later stage.

Validation Procedures

Great care is taken to avoid duplication. Available identifiers for mother and/or baby are checked against the database each time a new source of information is received. Regular duplicate checks are run using unique identifiers such as NHS number, hospital number or combinations of other identifiers. Other validation checks allow the correction of inconsistencies in all other data fields.