Congenital Malformations

Quality description

Relevance of statistical data

The Register of Congenital Malformations at the National Institute for Health and Welfare (THL) was established in 1963. The main purpose of the Register is to continuously monitor the prevalence and types of congenital anomalies for an early identification of any new environmental factors (teratogens) that potentially cause fetal defects, and for the prevention of congenital anomalies by influencing these factors. Statistical data are used for monitoring congenital anomalies nationally and regionally, for planning prenatal screening and diagnostics of fetal anomalies, as well as for treatment of congenital anomalies, and for conducting research on congenital anomalies.

THL collects data on congenital anomalies and maintains the Register of Congenital Malformations pursuant to the Act on the National Institute for Health and Welfare (668/2008, Section 2).

The Statistical Report of the Register of Congenital Malformations contains information on the number and prevalence rates (per 10 000 births) for detected congenital anomalies nationally and by areas of special responsibility of university hospitals. The Report contains the numbers of cases with con-genital anomalies detected in live births, stillbirths and selective terminations of pregnancy. Additionally, the proportion of annual cases among infant deaths is reported. The annual numbers and prevalence rates for certain internationally monitored congenital anomalies are given at the national level.

The Statistical Report aims to provide up-to-date information on the numbers and prevalence rates for congenital anomalies to health care professionals, administrators, planning officials and researchers working in the area of reproductive health and congenital anomalies, and any other people in need of such information.

Description of methods

The Register of Congenital Malformations receives data on congenital anomalies from hospitals, health care professionals and genetic laboratories. It also draws data from the Medical Birth Register, the Care Register for Health Care, the Register on Induced Abortions, all maintained by THL, and from the National Supervisory Authority for Welfare and Health (Valvira), as well as from the Cause of Death Statistics, maintained by Statistics Finland. When necessary, the diagnoses obtained from these data sources are confirmed by contacting the hospital or health care unit that have given treatment to the infant/fetus/woman. Notification of congenital anomaly should be made as soon as possible after the detection of a congenital anomaly after birth or selective termination of pregnancy. Although the Register mainly collects data from the first year of the infant, it also collects data on subsequently detected congenital anomalies of the child for statistics and research.

The Statistical Report includes statistics on live births and stillbirths in Finland when at least one major congenital anomaly has been detected. The report also includes statistics on selective terminations of pregnancy due to congenital anomalies.

The Statistical Report only gives information on major congenital anomalies as defined in the Register of Congenital Malformations, that is, structural anomalies, chromosomal defects and a few other congenital anomalies like congenital hypothyroidism. Congenital anomalies do not include dysfunction of organs or tissues, developmental disabilities, congenital infections, isolated minor dysmorphic features, normal variations and common minor congenital, isolated anomalies included in the exclusion list of the Register, or hereditary diseases and other diseases not associated with congenital anomalies. This practice complies largely with that of the European Surveillance of Congenital Anomalies EUROCAT. As the Register on Induced Abortions includes cases for the latter types of diagnoses, the statistics for selec-tive terminations of pregnancy are different in the statistical report on induced abortions and this report on congenital malformations.

Notifications of congenital anomalies are sent mainly in paper format. The data from the notification forms and other sources are stored in the electronic database for the Malformation Register. Data check-ups are made regularly, missing cases and case-specific data are added from other registers and any unclear cases and diagnoses are checked by contacting the treating hospitals.

Correctness and accuracy of data

Correctness of data depends on the quality of the data submitted by the data suppliers. Over time, the register may receive multiple notifications for the same infant or fetus. All notifications are included in the register and are used for supplementing and refining previously registered information on congenital malformations. The data in the Register of Congenital Mal-formations are compared with those in other registers and data sources.

The data content and the data collection practice of the Register of Congenital Malformations were revised in 1985, 1993 and 2005. From 1993 on-wards the data coverage and quality can be regarded as very good although there have been no coverage analyses or validation of the data since the 1993 revision. The prevalence rates for cases with congenital anomalies correspond to the normal prevalence rates described in the literature and reported internationally. The prevalence rates for different types of congenital anomalies have also been consistent with the findings of other national and international studies on congenital anomalies. Since 2005, data on congenital malformations have also been derived from the Care Register for Health Care, maintained by THL, which has further improved the total coverage of the Malformation Register.

As the Register of Congenital Malformations also draws data from other registers and confirms the diagnoses, its data sets are not complete until about two calendar years from the birth or selective termination of pregnancy.

Any errors identified in the statistics are corrected. The register data is continuously completed and corrected according to later notifications and any additional information that has been requested to the Malformation Register. The statistics are annually updated according to these changes, which are seen as small changes in the numbers and prevalence for the previous years of statistics and especially for the last reported year of statistics.

Timeliness and promptness of published data

The Statistical Report of the Register of Congenital Malformations is compiled annually by THL. As it is possible that congenital anomalies are not diagnosed in the first year of life, or their principal cause, such as a chromosomal defect is identified later, the numbers in the published annual statistics may change slightly over the years.

Accessibility and transparency/clarity of data

The Statistical Report is sent to hospitals and other units of health care submitting data to the Register, in addition to being published on the THL website. Statistical data is annually published in both national and international statistical publications (EUROCAT and ICBDSR).

Findata is authorised to disclose data in the Medical Birth register to researchers for scientific research purposes.

Comparability of statistical data

Over the decades there have been changes in the data collection and registration practice of the Register, and in the degree to which hospitals fulfil their notification obligations. With the development of prenatal screening and diagnostics, selective terminations of pregnancy for fetal anomalies have increased, the impact of which can be seen particularly when comparing statistics from the first decades to those published since the 1990s. The reform of the Act on Induced Abortion in 1985 and the redefinition of still-birth from January 1st 1987 onwards affect the comparability of data entered in the Register in different years and decades. The use of the Care Register for Health Care as data source for the Malformation Register in 2005 has improved the total coverage of the Register. Internationally, the statistics are of high quality and comparable.

In 2013, the Malformation Register started to use the numbers of births from the Medical Birth Register, THL, as denominators in prevalence calculations instead of the numbers of births from Statistics Finland. The Medical Birth Register and the Malformation Register both collect data on all births taken place in Finland, whereas Statistics Finland collects data on births of Finnish citizens that have taken place in Finland and abroad, but not on births of foreigners in Finland. In addition, the Malformation Register and the Medical Birth Register record deaths according to year of birth whereas Statistics Finland records deaths according to year of death. The concept of cases with congenital anomalies, and that of major congenital anomalies, as well as the definitions and classifications of major congenital anomalies, and the data content of the Register have remained for the most part similar during the years presented in the report.

Clarity and consistency

The Statistical Report uses established international concepts and classifications. They are mostly consistent with other national registers and databases that contain data on congenital anomalies.

For classifying and coding of the congenital anomalies in the register, the ICD-7, -8, -9 and -10 -versions of the International Classification of Diseases / WHO and, since 1993, an extension of the ICD-9 (retrospectively from 1986 onwards) have been used. The diagnoses are also given in verbal text, in English. The basic definitions for reproduction used have principally remained the same (Suomalainen tautien kirjaamisen ohjekirja. THL Opas 17/2012). The exclusion system, used by the Malformation Register, of minor anomalies and a few other abnormalities and diseases from statistical analyses complies largely with that of the European Surveillance of Congenital Anomalies / EUROCAT. The ATC-codes (Anatomic Therapeutic Chemical classification index) are used for medicines. The Classification of Municipalities of Statistics Finland for each year of publication of the report or of the year before is used in regional statistical analyses and is based on the woman’s home municipality.

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