North West Thames

History and Funding

Case registration began on 1 January 1990 and EUROCAT reporting began in 1996. Data transmission to ONS (the Office for National Statistics) began on 1 January 2000. The Registry is an active member of BINOCAR (British Isles Network of Congenital Anomaly Registers) and FOCAL (Follow-up of Congenital Anomalies Long Term).

Registry data continue to be used in many collaborative research projects as well as for local audit of prenatal screening and diagnostic programs. The Registry is funded by the London Genetics Commissioning Consortium.

Population Coverage

This is a hospital based registry (all mothers delivering in selected hospitals, irrespective of place of residence). However, in utero transfers to contributing hospitals due to an anomaly are excluded, whereas in utero transfers away from contributing hospitals following prenatal diagnosis of a congenital anomaly are included. It covers 17 NHS obstetric units in the North West Thames area (North West London, Hertfordshire and Bedfordshire).

These hospitals had about 48,000 births in 2003 representing about 8% of all births in England (98% of which occurred in hospital).

Sources of Ascertainment

Reporting is voluntary and multi-source.

Spontaneous reporting:
Midwives, obstetricians, paediatricians, and sonographers in contributing hospitals all complete forms when an anomaly is diagnosed pre or post natally. Each month, each contributing hospital downloads information about babies noted on the database to have anomalies and sends it to the registry. Each month, the regional cytogenetic laboratory downloads a list of all abnormal karyotypes for the registry. Information about deaths is provided by CEMACH (Confidential Enquiry on Maternity and Child Health) who share their forms and postmortem reports with the registry when the fetus/ baby had an anomaly. The regional fetal medicine unit sends copies of ultrasound reports. Information about postnatally diagnosed cardiac defects is provided by the unit that sees most such cases.

ASCAL (Audit of Screening for Chromosome Anomalies in London) shares information with the registry. Notifications from contributing hospitals to the National Congenital Anomaly Surveillance System are sent to the registry.

When information about a case is thought to be incomplete or incorrect, staff contact the appropriate source and endeavour to ensure that the information is correct and complete.

Birth certificates do not include notification of congenital anomaly.

Registration covers fetuses with prenatally diagnosed anomalies, affected fetuses spontaneously lost from 16 weeks gestation, babies diagnosed before their first birthday in the case of structural anomalies, and babies diagnosed at any time in the case of chromosome anomalies.

• Cardiac defects that have not been prenatally diagnosed are under ascertained.
• Between 1993 and the end of 2004, the registry excluded babies in whom the main diagnosis was hypospadias, polydactyly and syndactyly.
• Between 1996 and the end of 2004, the registry did not register cases where the main diagnosis was talipes.
• The Registry does not register fetuses in which the only anomalies reported are soft markers on ultrasound (such as dilated renal pelves, choroid plexus cysts, ventriculomegaly, bright bowel, golf balls in heart).
• Prior to 1996, ano-rectal atresia was not coded in a way that allowed it to be distinguished from other intestinal anomalies; so prior to 1996 cases of ano-rectal atresia were only included in total case counts of intestinal anomalies and not in case count of ano-rectal atresia.
• The code for indeterminate sex is almost never used, since cytogenetic and pathology investigations almost always determine the sex, and the coding is then adjusted as appropriate (such as malformation of external male genitalia).
• Prune Belly syndrome is not coded if underlying anomaly is known.
• Ascertainment was generally low in 1999 and in 2002.

Terminations of Pregnancy for Fetal Anomaly (TOPFA)

Termination of pregnancy is legal up to 24 weeks of gestation but if a serious congenital anomaly is diagnosed there is no gestational age limit. If the termination is carried out after 22 weeks and the condition is not lethal, a fetocide is usually performed prior to induction of labour. Terminations performed due to a congenital anomaly are reported to the register by all the same sources which report term deliveries. Information is collected on how and when anomalies were diagnosed, the indication for any invasive tests that were done and why prenatal karyotyping was not done.

Stillbirth and Early Fetal Deaths

The official stillbirth definition is: a child born with no signs of life after complete expulsion from the mother after the 24th week of pregnancy (there is no weight limit). All stillbirths are registered. Early fetal deaths/spontaneous abortions are included with a lower limit of 16 weeks for chromosome anomalies unless they were prenatally diagnosed.

Autopsy rates were as follows in 2000: 66% in stillbirths, 47% in induced abortions (some autopsies not done include early terminations of pregnancy with dilatation and curettage), 46% in early neonatal death (0-7 days), 59% in later deaths 1 week to 1 year and 66% in deaths with congenital anomaly.

Exposure Data Availability

Chronic illness in mother, pregnancy induced condition in mother, acute maternal illness during pregnancy, therapeutic and recreational drugs taken around conception and during pregnancy, invasive tests in pregnancy, smoking habits, alcohol abuse, consanguinity and post code of residence. Post code of residence is very well reported. Other exposures are thought to be under-reported.

Denominators and Controls Information

As the numerator is hospital based, the denominator is the births and terminations of pregnancies in the contributing hospitals. Hospitals have a computerized database in which information is stored on all births. This database holds much of the same information about babies as stored on the registry database and is one of the reporting sources to the register.

Address for Further Information

Congential Malformations Register Room 8W015,
Perinatal Public Health Northwick Park Hospital,
Watford Road
Harrow, HA1 3UJ, United Kingdom
 

Last updated: August 2007