National Register of Congenital Anomalies

The Register of Congenital Anomalies is, in the case of born children, part of the National Medical Birth Register. Foetal damage and chromosomal aberrations or abnormalities found in neonatals (newborn) as well as aborted fetuses are reported to this register, so that any increase can be detected as quickly as possible.

In addition to surveillance, the Register aims to study long-term changes in the incidence of specific injuries and deviations over time. For those analyses, the information in the Register of Congenital Anomalies is combined with information in the Medical Birth Register, and the Patient Register up to one year of age.

Contents of the Register

The Register contains data on neonatal births (newborn), live births and stillbirths with a gestation period of at least 22 completed weeks of pregnancy and which have congenital malformations, deformities or chromosomal abnormalities. A separate register includes anonymized data on fetuses aborted due to foetal damage or chromosomal abnormalities.

Register content, as regards newborns, is based on information from medical records of the mother and baby. The key variables are the mother's personal ID number (not in the case of terminated pregnancies), the child's date of birth, sex, weight and height at birth, length of pregnancy and diagnosis of developmental anomalies.

For terminated pregnancies, the woman's age (grouped into five-years classes), as well as indication and method of prenatal diagnosis, are recorded.

The registration of neonatal births and aborted fetuses is limited to more serious diagnoses. The International Classification of Diseases (ICD10) is used to classify diagnoses.


The monitoring of developmental anomalies started in 1964, following the Thalidomide scandal. This led to the creation of a birth-defect register, which, in 1973, became part of the National Medical Birth Register for newborns.

The Register changed in 1999, when a new reporting form was introduced with a list of diagnoses of foetal damage and chromosomal abnormalities in accordance with the Swedish version of ICD-10. At the same time, the content of the Register was expanded to include foetuses from pregnancies terminated because the foetus had a malformation or chromosomal abnormality. It also became obligatory to report heart defects verified by ultrasound.

In April 2007, the name was changed from the Register of Birth Defects to the National Register of Congenital Anomalies. An alignment with international standards took place on 1 July 2008, when the definition of a child was changed from 28 completed weeks of pregnancy to 22 completed weeks of pregnancy for stillbirths, thus extending the reporting obligation to children born in weeks 23–28. All live births must be reported to the National Medical Birth Register, regardless of the length of pregnancy.

Quality and Non-response

As of 2013, children with developmental anomalies reported to the National Register of Congenital Anomalies are linked to the National Medical Birth Register as well as to the National Patient Register. Regular cross-referencing is also carried out for drug exposure in early pregnancy in relation to children with developmental anomalies.

In the case of abortion, however, no searches or additions can be made for unreported cases, as the woman's personal ID number is not recorded. Nor can cross-reference be made to other registers to study, for example, drug exposure.

The Register has a relatively high non-response rate for fetuses after induced abortions due to developmental anomalies. The non-response rate in these cases is estimated at approx. 35–50 per cent. In the case of neonatals, the non-response rate is lower. However, as long as non-response is random, it has little impact on assessments of risk factors. The absence of a data point only becomes important when trying to determine how common a phenomenon is.

Confidentiality of the Register

The information in the register is protected by so-called absolute confidentiality, which is the strongest confidentiality protection provided by law. Exceptions only apply to data needed for research or statistical purposes and for data that cannot be directly attributed to an individual person. In these cases, the information can be disclosed if it is clear that doing so causes no damage or harm to the person to whom the information relates or any close relative. Confidentiality also applies within the National Board of Health and Welfare.

Register data are physically protected in restricted areas.

Statistics based on the Register

If you are interested in statistics based on Register of Congenital Anomalies data, see Ordering data and statistics (only available in Swedish).

Related sources


National Register of Congenital Anomalies
Phone number: +46 75 247 30 00