Quality Report of the OSF Publication Series
Congenital anomalies
Relevance of statistical data
The Register of Congenital Malformations at the National
Institute for Welfare and Health (THL) was es-tablished in 1963.
The main purpose of the Register is to continuously monitor the
prevalence and kind of congenital anomalies for an early
identification of any new environmental factors that potentially
cause foetal defects, and for the prevention of congenital
anomalies by influencing these factors (monitoring / surveillance).
Since 1993, the production of statistics for national and
international purposes has become an increasingly important element
of the Register's activities. Such statistical data are used for
monitoring congenital anomalies nationally and regionally, for
planning prenatal screening and diagnostics, as well as treatment
of congenital anomalies, and for conducting research on congenital
anomalies.
The Statistical Report of the Register of Congenital
Malformations contains information on the number and prevalence
rates (per 10 000 births) of congenital anomalies detected in
stillbirths or in live births, on an annual basis, both nationally
and by hospital district. The national-level data gives the numbers
of cases with congenital anomalies among perinatal deaths and
infant deaths, as well as the percentages of such cases of all
infant deaths at the same age. In addition, the Report contains
statistical data on major foetal malformations and other birth
defects detected in selective terminations of pregnancy, and
analyses the impact of such terminations on the national prevalence
of cases with congenital anomalies. The annual numbers and
prevalence rates of certain internationally monitored congenital
anomalies are given at the national level, while a more detailed
analysis is presented of neural tube defects, Down's syndrome and
orofacial clefts. The statistics begin from 1993, after which year
the Register data have had an adequate coverage and
reliability.
The Statistical Report aims to provide up-to-date information on
the numbers and prevalence rates of 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.
The collection of data is based on the Act on the Statistical
Actions of the National Research and Devel-opment Centre for
Welfare and Health (STAKES; currently the National Institute for
Health and Welfare, THL) (409/2001), as well as on the Act on
Nation-wide Health Care Registers (556/1989) and the subsequent
Statute (774/1989).
Description of methods used in statistical
research
The Register of Congenital Malformations receives data on
congenital anomalies from hospitals, health-care professionals and
cytogenetic laboratories. It also draws data from the Medical Birth
Register, the Care Register for Health Care (including Information
on Outpatient Services in Specialised Health Care), the Register on
Induced Abortions, and the Register of Visual Impairment, all
maintained by THL, as well as from the data provided by the
National Supervisory Authority for Welfare and Health (Valvira),
and from the Cause of Death Statistics, maintained by Statistics
Finland. The diagnoses obtained from these data sources are
confirmed by contacting the hospitals that have given treatment to
the infant/foetus. Notification of congenital anomaly should be
made as soon as possible after the detection of a congenital
anomaly after birth or termination of pregnancy. Although the
Register mainly collects data from the first year of the infant for
monitoring, it also collects data on subsequently detected
congenital anomalies for statistics and research.
The Statistical Report shows statistics on cases with congenital
anomalies included into the Register of Congenital Malformations,
i.e. live births, stillbirths or selective abortions in Finland
with at least one detected major congenital anomaly and with a
mother who has been resident in Finland at the time of the delivery
and also during most of the pregnancy.
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 congenital hypothyroidism. Major congenital anomalies do not
include hereditary diseases and other diseases not associated with
congenital anomalies, dysfunction of organs or tissues,
developmental disabilities, congenital infections, isolated minor
dysmorphic features, normal variations and common less significant
congenital anomalies included in the exclusion list of the
Register. This practice complies largely with that of the European
Registers of Congenital Anomalies EUROCAT.
From the notification forms and other sources, the data are
stored in the Register electronically. The register is maintained
by THL pursuant to the Act on Nation-wide Health Care Registers
(566/1989) and Section 8 of the subsequent Statute (774/1989). Data
check-ups are made regularly, missing cases and case-specific data
are added from the Medical Birth Register, for instance, and any
unclear cases and diagnoses are checked and ascertained by
contacting the treating hospitals.
Correctness and accuracy of data
The data are correct if they have been reported correctly.
Several notifications to the Register may be concerned with the
same infant or foetus, specifying previously received data and
ascertaining diagnoses of congenital anomalies. In case of
uncertainty, the treating hospitals are contacted in order to check
the data. The Register data are also compared with data from the
Medical Birth Register, the Care Register for Health Care
(including Information on Outpatient Services in Specialised Health
Care), the Register on Induced Abortions and the Register of Visual
Impairment, all maintained by THL, with data provided by the
National Supervisory Authority for Welfare and Health (Valvira) as
well as with data from the Cause of Death Statistics, maintained by
Statistics Finland, whereby case-specific data are complemented,
any missing cases with congenital anomalies are added to the
Register, and diagnoses are confirmed by contacting the treating
hospitals.
The data content and the data collection practices of the
Register of Congenital Malformations were revised in 1985, 1993 and
2005. From 1993 onwards the data coverage can be regarded as very
good although there have been no coverage analyses since the 1993
revision. The prevalence of cases with congenital anomalies
corresponds to the normal prevalence described in the literature
and reported internationally. The prevalence rates of 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 statistics on Information on Outpatient
Services in Specialised Health Care, which has further improved the
total coverage of the Malformation Register to some extent.
As the Register of Congenital Malformations also draws data from
other registers, its data sets are not complete until after two
calendar years from the birth, whereby the final data are published
in the Statistical Report. In addition, the Register issues a
report on preliminary data on congenital anomalies after one
calendar year from the birth or the selective termination of
pregnancy. As regards most cases with severe congenital anomalies,
the coverage of the preliminary statistics has been found to be
over 90 per cent. The preliminary statistical data concerning a
majority of internationally monitored types of anomalies show an
almost complete coverage. Preliminary statistics are complemented
during the following calendar year, being subsequently published in
the Statistical Report.
Any errors identified in the statistics will be corrected.
Timeliness and promptness of published data
The Statistical Report of the Register of Congenital
Malformations is compiled annually by THL. In gen-eral, it is
published in March or April. From 1993 onwards, the statistics are
complete, excluding the two previous calendar years before the
publication of the Report only. The preliminary data are from end
of the first calendar year after the birth, termination of
pregnancy or spontaneous abortion. As it is possible that
congenital anomalies are not diagnosed or their principal cause,
such as a chromosomal defect, is not identified until at a later
stage in the infant's life, the numbers in the final annual
statistics may change slightly over the years - this, however, only
concerns a few individual cases.
Accessibility and transparency/clarity of
data
The Statistical Report is sent to hospitals and other units
submitting data to the Register, in addition to being published on
the THL website at
http://www.thl.fi/statistics/congenitalmalformations.
The text material of the Report describes major findings and
specifies concepts, definitions, symbols and methods. In order to
give a better general idea of the situation longer time series have
been used in some of the figu-res than elsewhere in the statistics
of the Statistical Report. The graphs of the time series have been
smoothed by the Microsoft Excel data analysis software in order to
show the continuous formation of congenital anomalies. Further
information on the numbers and prevalence rates of congenital
anomalies is available from the Register.
Comparability of statistical data
The statistical data collected after the 1993 revision of the
Register of Congenital Malformations are not directly comparable
with the Register's earlier data, as the revision considerably
improved the coverage and quality of the data compared with the
data for 1963-1992. In addition to changes in the data collection
and registration practices of the Register, and in the degree to
which hospitals fulfil their notification obligations, there have
been changes in the definitions, classifications, coding systems,
diagnostics and treatment of congenital anomalies and related
mortality rates over the decades. With the development of prenatal
screening and diagnostics, selective terminations of pregnancy have
increased. The impact of these developments has been seen
particularly as regards certain severe congenital anomalies. In the
late 1980s, the coverage of the Register was considerably reduced
as a result of the 1985 revision of the Register. Moreover, the
reform of the Act on Induced Abortion in 1985, and the redefinition
of stillbirth from January 1st 1987 onwards affect the
comparability of data entered in the Register in different years
and decades. The 1986-1992 data of the Register are being
complemented by congenital anomaly data drawn from other registers.
The use of the statistics on the Information of Outpatient Services
in Special-ised Health Care as data source for the Malformation
Register in 2005 has improved the total coverage of the Register to
some extent, but has not affected the coverage of severe
malformations in the Register.
Beginning from 1993, the annual statistical data presented in
the Statistical Report are mutually comparable; the modification of
the data collection practices in 2005 does not reduce the
comparability of data on severe malformations. Internationally, the
statistics are of high quality and comparable. The prevalence rates
of preliminary statistics are comparable with the final annual
statistics. In some hospital districts, the degree of meeting the
notification requirement is lower than usual, as a result of which
the total coverage of cases with congenital anomalies may be
somewhat lower within these districts than elsewhere in the
country.
The concept of cases with congenital anomalies (births,
terminations of pregnancy or spontaneous abortions involving
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
unchanged since 1993. The basic definitions used (ICD-10) have
remained the same.
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. |