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European Journal of Public Health, 1–9
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.........................................................................................................
Linking databases on perinatal health: a review of the
literature and current practices in Europe
M. Delnord
1
, K. Szamotulska
2
, A.D. Hindori-Mohangoo
3,4
, B. Blondel
1
, A.J. Macfarlane
5
,
N. Dattani
5
, C. Barona
6
, S. Berrut
7
, I. Zile
8
,R. Wood
9
, L. Sakkeus
10
, M. Gissler
11
, J. Zeitlin
1
,
and the Euro-Peristat Scientific Committee
1 INSERM, UMR 1153 Obstetrical, Perinatal and Pediatric Epidemiology Research Team (Epope
´), Center for Epidemiology
and Statistics Sorbonne Paris Cite
´, DHU Risks in pregnancy, Paris-Descartes University, Paris, France
2 Department of Epidemiology and Biostatistics, National Research Institute of Mother and Child, Warsaw, Poland
3 Netherlands Organization for Applied Scientific Research, TNO Healthy Living, Department Child Health, Leiden, The
Netherlands
4 Anton de Kom University of Suriname, Faculty of Medical Sciences, Department Public Health, Paramaribo, Suriname
5 Centre for Maternal and Child Health Research, City University London, London, UK
6 General Directorate of Public Health, Generalitat Valenciana, Valencia, Spain
7 Swiss Federal Statistical Office, Section Health, Neucha
ˆtel, Switzerland
8 Centre for Disease Prevention and Control of Latvia, Riga, Latvia
9 Information Services Division, NHS National Services Scotland, Edinburgh, Scotland, UK
10 Estonian Institute for Population Studies, Tallinn University, Tallinn, Estonia
11 Information Services Department, THL National Institute for Health and Welfare, Helsinki, Finland
The members of the Euro-Peristat Scientific Committee are listed in the Acknowledgements.
Correspondence: Marie Delnord, INSERM UMR 1153, Obstetrical, Perinatal and Pediatric Epidemiology Research Team
(Epope
´), Research Center for Epidemiology and Biostatistics Sorbonne Paris Cite
´(CRESS), Maternite
´de Port Royal,
53 Avenue de l’Observatoire, 75014 Paris, France, Tel: +33 1 42 34 55 86, Fax: +01 43 26 89 79,
e-mail: Marie.delnord@inserm.fr
Background: International comparisons of perinatal health indicators are complicated by the heterogeneity of
data sources on pregnancy, maternal and neonatal outcomes. Record linkage can extend the range of data items
available and thus can improve the validity and quality of routine data. We sought to assess the extent to which
data are linked routinely for perinatal health research and reporting. Methods: We conducted a systematic review
of the literature by searching PubMed for perinatal health studies from 2001 to 2011 based on linkage of routine
data (data collected continuously at various time intervals). We also surveyed European health monitoring pro-
fessionals about use of linkage for national perinatal health surveillance. Results: 516 studies fit our inclusion
criteria. Denmark, Finland, Norway and Sweden, the US and the UK contributed 76% of the publications; a further
29 countries contributed at least one publication. Most studies linked vital statistics, hospital records, medical birth
registries and cohort data. Other sources were specific registers for: cancer (70), congenital anomalies (56), ART
(19), census (19), health professionals (37), insurance (22) prescription (31), and level of education (18). Eighteen of
29 countries (62%) reported linking data for routine perinatal health monitoring. Conclusion: Research using
linkage is concentrated in a few countries and is not widely practiced in Europe. Broader adoption of data
linkage could yield substantial gains for perinatal health research and surveillance.
.........................................................................................................
Introduction
International comparisons of perinatal health indicators provide
valuable evidence for public policy planning and practice by
allowing benchmarking across countries, and revealing the
diversity in clinical practice related to antenatal and delivery
care.
1,2
In Europe, recent results from the European Perinatal
Health Report 2010 (EPHR 2010) showed wide differences in
health outcomes and indicators of clinical practice. For example in
2010, stillbirth rates ranged from 2.0 to 4.0 per 1000 births and
cesarean section rates ranged from 13% to 47% of total births.
1,3–5
International comparisons are limited by the quality and com-
pleteness of information held in national data systems however.
The EPHR 2010, which reported on population-based aggregate
data from 26 EU Member States, plus Iceland, Norway
and Switzerland
6
showed gaps in data availability of many
key indicators. For instance, only 19 out of 29 countries had
data on the gestational age distribution of neonatal deaths, 17
on smoking during pregnancy and 5 on severe maternal morbidity.
7
To compile the Euro-Peristat indicators, countries used
multiple data sources: birth certificates, death certificates, medical
birth registers, specific registers or audits, hospital discharge
data, professional databases and surveys. These varied in their
inclusion criteria and data quality, raising questions about
comparability.
1,6
Record linkage between health, civil and administrative data
systems is one way to increase the completeness, quality and
breadth of data available for perinatal health monitoring and
research. Linkage is the term used to describe the process of
merging individual records from two or more datasets in order to
extend the range of data items available.
6
Linked data have been used
to generate knowledge and investigate the association between
population risk factors and a wide array of both maternal
7,8
and
infant health outcomes.
9–11
However, there is currently no informa-
tion on the extent to which linkage is used in Europe for surveillance
and research. In this study, our objectives were to assess: the types of
linkage done for perinatal health research and monitoring, the
maternal and infant health themes and outcomes explored in
research using linkage, and potential gaps in current record
linkage practices in European countries.
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Methods
This study was based on data from a systematic review of publica-
tions on linkage, and on information collected within the Euro-
Peristat project about the use of linkage in routine perinatal health
monitoring.
Review of publications based on linked data
from routine sources
Search strategy
We searched PubMed for perinatal health studies based on linkage of
routine data sources published between 2001 and 2011. Routine data
sources are those that collect information continuously or regularly
(in the case of surveys). We used the following key works: data
linkage, perinat
,
matern
, link
, registr
, medical record linkage,
infant newborn and birth certificates. Publications were screened
by the first author based on information provided in the titles and
abstracts. We identified 990 studies from which we excluded
conference reports, summaries and reviews. We did not include
studies with data that are not regularly repeated. We included
research related to the perinatal period: pregnancy, delivery and
the post-partum, which linked two or more routine datasets
together or paired mother and newborn records within the same
data collection system. Studies linking pregnancy or birth cohorts
to routine datasets were included. To increase coverage, we
contacted Scientific Committee (SC) members of the Euro-Peristat
network for any additional research articles that we might have
missed from their countries. Our final sample included 516
studies. More information on search terms and the database are
available from the authors on request.
Data extraction
From each study, we extracted the types and number of routine data
sources used, the main outcome variables, the dependent variables,
country of origin and year of publication. Principal types of sources
were: civil registration (birth and death certificates), hospital
discharge data (i.e. admissions, inpatient and other medical
records) and medical birth registers (which hold birth data
augmented with clinical information about each delivery and
birth).
1
We described how linkage was used in perinatal health research by
classifying publications according to themes and linkage types within
countries and by year. We categorized studies based on their
outcome variables into the following research themes: (i) fetal,
neonatal and child health, (ii) maternal health and (iii) methods –
this theme included studies focused on validating data through
record linkage use, or on usage of specific data linkage techniques
such as probabilistic vs. deterministic methods. We further assessed
which of our included studies were longitudinal. We flagged studies
as ‘longitudinal’ when researchers studied the impact of health
events outside the perinatal period (i.e. exposure to environmental
risk factors during pre-conception) on outcomes during the
perinatal period (i.e. birth weight), or when researchers studied
the influence of perinatal risk factors (i.e. preterm birth) on longer
term maternal or child health outcomes (i.e. educational
attainment). Data extraction was carried out by the first author
and validated by the co-authors.
Analysis
We identified recurrent and less common linkages based on the
types of data sources used, such as linkage of vital statistics data
and medical birth register data, and how often these were linked
across studies. All original data sources were accounted for in the
analyses. In the Netherlands for instance, birth data held in
the medical birth register are compiled from data held in the
obstetric, paediatric and neonatal registers. Similarly, linked
datasets such as the Oxford Record Linkage Study were described
in terms of their constituent datasets (i.e. linkage of civil registration
data, hospital discharge data and domiciliary midwives case notes).
Data were analyzed using STATA 13.0 software (StataCorp LP,
College Station, TX). We used the software to describe the overall
characteristics of the studies included in this review such as the time
period, country, or the topic area, and also to identify and keep track
of the different possible types of linkages available in the literature
and their associated study outcomes.
Data on routine linkages from the Euro-peristat
network
We used data collected for the EPHR 2010 supplemented by
additional information from the Euro-Peristat Scientific
Committee (SC). Euro-Peristat indicators were compiled from
routine aggregate data available from population-based registers.
As part of the data collection exercise, SC members were asked to
describe the characteristics of their national data systems and in
particular: inclusion criteria, year in which the data source began,
estimates of coverage (i.e. nationals vs. residents), capacity and use
of linkage, and plans to modify or extend the data source.
SC members were also asked to confirm the availability in routine
of the most prevalent linkage types identified in our review of the
literature: (i) linkage of birth and death certificates, (ii) vital
statistics and medical birth register data, (iii) medical birth register
data and hospital discharge data and (iv) vital statistics and hospital
discharge data. In our study, vital statistics data included: birth cer-
tificates, death certificates and/or data on causes of death. We
identified hospital discharge data, as all data extracted from
admissions, inpatient care or other clinical records (i.e. maternity
records or pediatric records). SC members could specify any other
routine linkage available in their country which might not have been
recorded for the Euro-Peristat data collection.
Results
Table 1 shows that there were wide variations in the use of record
linkage in perinatal health research between 2001 and 2011. There
was a very strong increase in publications which linked perinatal
health data over time and there were also large differences in the
number of studies each country contributed, the number of routine
data sources used and the types of linkage which were done.
The use of record linkage increased steadily between 2001 and
2011 and 41% of the articles were published between 2009 and
2011. Three quarters of the studies were from a selected few
countries namely the Nordic countries (in particular Denmark,
Finland, Norway and Sweden), the US and the UK which
contributed 43%, 19% and 12% of the publications, respectively.
Australia and Canada contributed another 12% of the studies but
other countries contributed many fewer; twenty two European
countries published between 1 and 11 studies accounting all
together for about 5% of our study sample. We compared the dis-
tribution of studies by groups of countries (Nordic, US, UK and
other) between two time periods (2001–2006 and 2007–2011) and it
was similar (P= .224). The number of routine data sources used
varied between 1 (i.e. when mother and newborn records were
paired within the same data source) and 7 (mainly in the Nordic
countries), but most studies used 2–3 data sources. The majority of
studies merged vital statistics data and hospital discharge data, but
other linkage types were also identified.
Table 2 shows the wide variety of linkage types performed in
perinatal health research between 2001 and 2011; we display the
distribution of perinatal health record linkage studies for which at
least two distinct types of routine data sources were used. We
identified 16 types of data sources in the literature and tabulated
all two-by-two linkages between these data sources as well as the
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total number of studies in which each type of data source was used.
For example, in a Swedish study that linked three population-based
data sources (the Medical birth register (MBR), hospital discharge
data and the Prescription drug register),
12
we counted the following
two-by-two linkages: (i) MBR with Hospital discharge data, (ii)
MBR with Prescription drugs register and (iii) Prescription drugs
register with hospital discharge data. Linkages were distributed
unevenly across routine data sources. The 254 linkages involving
vital statistics data were the most common. Next, 219 linkages
with medical birth registers and 203 with hospital discharge data
provided more detailed data on pregnancy, delivery and the
postpartum; and finally, studies linking socio-economic data from
other sources, e.g. census data, were the least prevalent.
In table 3, we present the themes explored in the literature using
linkage based on studies’ main outcome variables and their timing of
occurrence. About 62% of studies focused on infant health
outcomes, 20% of studies focused on maternal health outcomes
and 14% of studies focused on use of linkage to validate data
quality and completeness, and on the accuracy of methods for
linking perinatal data. Nearly 40% of maternal and infant health
studies were longitudinal and examined health issues and associ-
ations outside of the perinatal period.
Among the 342 infant health studies, 60% focused on perinatal
issues such as fetal, neonatal or infant mortality, congenital
anomalies, preterm births, births small-for-gestational age and low
birth weight. Linkage techniques were also used to study longer term
outcomes such as child health, need for health services, highest level
of education, motor and cognitive development of babies born at-
risk of adverse outcomes such as very preterm births, diabetes,
asthma and adult mental health issues. For example in an English
study, a cohort of 248 612 births from 1970 to 1989 in parts of the
former Oxford Region in Southern England was linked to records of
subsequent hospital admission for 4017 children with asthma up to
1999.
13
A study in Denmark looked at the association between
congenital anomalies and social position among 19 874 women.
14
A Norwegian study analyzed the mental health outcomes of
children with congenital heart defects from age 6–36 months in a
cohort of 44 104 children.
15
Linkage techniques have also been
Table 2 Distribution of perinatal health record linkage studies for which at least two distinct types of routine data sources were used;
N= 2172 two by two linkages in N= 516 studies
4
Data Source no. 1
Data Source n2 VS MBR HD POP Cohort Cancer CA PROF DRUGS ID PSY Insurance ART Census EDU Screening
Vital Statistics (VS)
a
–
Medical birth register (MBR) 45 –
Hospital discharge data (HD)
b
90 89 –
Other population register (POP) 45 52 50 –
Cohort study 18 31 27 14 –
Cancer register 42 11 21 10 11 –
Congenital anomalies register (CA) 32 22 19 6 6 4 –
Health professional register (PROF)
c
13 26 18 8 2 3 9 –
Prescription drugs register (DRUGS) 522 15 6 5 1 53 –
Illness/Disability register (ID) 525 7 4 1 2 35 2 –
Psychiatric register (PSY) 97 811 7 3 33 2 1–
Insurance 14 8 4 4 0 1 2 0 3 0 0 –
ART register (ART) 610 8 3 1 3 20 1 00 1 –
Census 12 9 5 11 0 3 0 1 0 0 0 1 0 –
Register on level of education (EDU) 918 4 6 1 0 20 0 10 1 1 1 –
Screening register 10 6 7 0 2 1 5 3 0 0 1 0 0 0 0 –
N 2x2 linkages
d
355 381 372 230 126 116 120 94 70 56 55 39 36 43 44 35
N studies
d
254 219 203 96 80 70 56 37 31 29 22 22 19 19 18 18
a: Birth records, death records and cause of death data.
b: Hospital discharge data includes inpatient data and other medical records.
c: Includes registries with data on pregnancy, delivery and/or the postpartum maintained by health professionals (i.e. Midwives’ register of
New South Wales, NVK: Paediatric Association of the Netherlands).
d: Studies sometimes linked more than 2 databases which explains why there are more 2 2 linkages than number of studies per data source.
Table 1 Description of perinatal health record linkage studies
included in review, N= 516
Characteristics of studies N %
Year of publication
2001–2002 48 9.3
2003–2004 58 11.2
2005–2006 90 17.4
2007–2008 112 21.5
2009–2011 208 40.5
Country
Nordic countries
a
223 43.2
US 99 19.2
UK 63 12.2
Australia 43 8.3
Canada 18 3.5
Taiwan 14 2.7
Brazil 14 2.7
Netherlands 12 2.3
Other countries with 1–11 studies
b
30 5.8
No. of data sources
1
c
91.7
2 293 56.8
3 134 26.0
4 or more 80 15.5
Linkage types
Vital statistics: birth and death certificates 101 19.6
Vital statistics and hospital discharge data
d
90 17.4
Medical birth register (MBR) and hospital discharge data 89 17.2
Vital statistics and MBR 45 8.7
Other
e
191 37.0
Longitudinal study 257 50.0
a: Nordic countries include Denmark, Finland, Norway and Sweden.
b: Countries include 21 EU member states, Switzerland, Singapore,
China, Cuba, Ghana, Malawi, Mexico and New Zealand.
c: Linkage of mother and baby records within the same registry, or
linked birth and death files from the same data source.
d: Hospital discharge data includes inpatient data and other
medical records.
e: ‘Other’ linkage types exclusive to studies for which vital statistics,
medical birth registry and hospital discharge data were not
included in the record linkage (cf. Table 2).
Linking databases on perinatal health 3of9
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particularly useful for childhood cancer research
16–25
and to study
specific conditions such as: Legg Calve Perthes disease,
26
cerebral
palsy,
27–30
epilepsy,
31–34
neonatal encephalopathy,
35
infantile hyper-
trophic pyloric stenosis
36,37
and schizophrenia.
38–49
Among the 101 maternal health studies, 57% examined mothers’
health status during the perinatal period; these publications focused
on maternal morbidity (i.e. multiple sclerosis,
50–53
thyroiditis,
54,55
toxoplasmosis
56
), mortality, obstetric management, mode of delivery
and other pregnancy complications. Record linkage was also used
to study women and mothers’ long term health outcomes. For
example, a study in Sweden examined reproductive patterns and
pregnancy outcomes of women with congenital heart disease in a
population-based study of 500 245 women.
57
Other studies looked at
pregnancy outcomes and selected conditions later in life such as
hypertension and diabetes.
Among studies on methods in record linkage as applied to
perinatal health, 42 focused on improvement of data quality, and
other studies focused on the ascertainment of maternal and infant
health outcomes, 13 and 18, respectively. Among these methods
studies, 36 validated population estimates and 23 validated data
items. A further 14 focused on the methods for extending routine
data to serve other functions such as pharmacological surveillance
and research on child abuse. From these studies, we identified
procedures related to the general ascertainment of births,
including underreporting of births at early gestations, completeness
of population coverage and identification of multiple births. There
were ten which related to procedures to identify maternal deaths, 7
relating to the ascertainment of fetal and infant deaths and 7
network or register audits. Some studies focused on validation of
data items: 18 on the presence and characteristics of birth defects,
one on assisted reproductive techniques (ART), three on obstetric
history and one on social characteristics. A further 26 studies
focused on metrics to validate deterministic and probabilistic
linkages.
Table 4 provides an overview of routine perinatal health linkages
performed in countries reporting data to Euro-Peristat. Among the
29 European countries participating in the Euro-Peristat project, 18
report using at least one type of linkage for routine statistics and 11
do not. Supplementary Annex SI provides more information on
linked sources used in the 2010 report. Some countries such as
Denmark can link their data systems for research projects but
these linkages are not routine. Countries which currently merge
national level datasets for perinatal health surveillance essentially
link birth and death data but the data sources used for this type
of linkage vary. Cyprus, Finland, Latvia, Luxembourg, Malta,
Norway, Sweden, UK Scotland, Iceland and the Czech Republic
link data from their medical birth registers with death certificates.
Austria, Belgium, Estonia, France, Germany, Poland, Switzerland
and UK: England and Wales routinely link their birth and death
data from vital statistics data sources alone. Similarly, data on
births and from hospital discharge systems can be linked using
vital statistics as in Scotland and Sweden, or data from a medical
birth register as in Luxembourg. Seven countries carry out national
linkages with hospital discharge data although in Germany this is
done at the regional level only, in Lower Saxony. Other reported
linkages involve congenital anomaly registers, cause-of-death data,
registers on level of education, or are done at the regional-level only.
These other linkages are exclusively performed in countries where
birth and death data are routinely linked at the national level.
Table 4 Routine linkage of perinatal health data in 2014 in 26 EU
Member States
1
, Norway, Switzerland and Iceland by type of data
linked
2
Countries participating in Euro-Peristat
Type of linkage
2
N % Countries
Births and hospital
discharge data
Birth certificates &
hospital discharge
data
2 7% Sweden, UK: Scotland
1
Medical birth register &
hospital discharge
data
6 21% Estonia, Finland, Luxembourg,
Sweden, UK: Scotland
1
, Iceland
Births and deaths data
Medical birth register &
neonatal/infant death
certificates
10 34% Cyprus, Finland, Latvia,
Luxembourg, Malta, Norway,
Sweden, UK: Scotland
1
,
Iceland, Czech Republic
Birth certificates &
neonatal/infant death
certificates
10 34% Austria, Belgium, Estonia, France,
Germany, Poland, Sweden,
Switzerland, UK: England and
Wales
1
, UK: Scotland
1
Medical birth register &
birth certificates
8 28% Estonia, Finland, Slovenia, Malta,
Norway, Sweden, UK:
Scotland
1
, Iceland
Other linkages
3
10 34% Belgium
a
, Finland
b
, France
c
,
Germany
d
, Malta
b
, Norway
a
,
Sweden
a,e,
Switzerland
a
,
Netherlands
f
, UK: Scotland
1,g
No routine linkage 11 38% Denmark, Greece, Hungary,
Ireland, Italy, Lithuania,
Portugal, Romania, Slovakia,
Spain, UK: Northern Ireland
1
,
UK (national)
1
1
UK’s four constituent countries: England, Wales, Northern Ireland
and Scotland compile data separately.
2
Some countries perform several types of linkages.
3
Routine linkages with: a. population registers, b. congenital
anomaly registers, c. vital statistics and cause-of-death data,
d. regional data sources only, e. registers on level of education,
f. health professional registries, g. any other national level health
database on children or mothers.
Table 3 Primary outcomes in perinatal health studies using record
linkage, N= 516
Theme Main outcomes N %
Fetal, neonatal
and child health
Perinatal period 152
Stillbirth, neonatal or infant
mortality
61 11.8
Congenital anomalies 20 3.9
Preterm birth, SGA, LBW and
other health outcomes with or
without mortality
71 13.8
Longer term outcomes 190
Child health and development 84 16.3
Cancer 33 6.4
Auto-immune diseases: diabetes,
asthma, allergies during
childhood or adulthood
23 4.5
Other adult health issues 50 9.7
Maternal health Perinatal period 40
Maternal mortality/severe
morbidity
81.6
Other maternal health outcomes 25 4.8
Mode of delivery/obstetric
management
71.4
Longer term outcomes 61
Women’s health pre-conception
or more than 1 year post delivery
16 3.1
Cancer 19 3.7
Auto-immune diseases 3 0.6
Other health issues 23 4.5
Methods studies
a
73 14.1
a: Includes studies focused on validating data through record
linkage use, or on usage of specific data linkage techniques.
SGA: small for gestational age, LBW: low birth weight
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Discussion
By harmonizing data systems, and ensuring completeness of
coverage, record linkage increases the information available about
each birth and can enhance the quality of perinatal health data.
However, our review shows that this technique is largely under-
used in Europe: 11 out of 29 countries do not routinely link data
on births and only 18 countries perform basic linkages such as
linking birth and death certificates. Also, linkage studies were
concentrated in a small set of countries; almost half of the studies
published from 2001 to 2011 originated from the Nordic countries
(N= 223). In the Nordic countries, the types of linkages performed
for perinatal health surveillance were also more diverse than
anywhere else in Europe.
Historical differences in health information capacity between
countries may explain some of the variation in record linkage use
in Europe. In England and Wales for instance, initiatives to link
birth and death certificates began in 1950 in order to maximize
the value of existing routine data and develop capacity for analyses
of perinatal and infant mortality
58
—this linkage has been routine
since 1975. The Oxford Record Linkage Study (ORLS), which started
in the 1960s was seminal as both a research tool and a means to
improve the quality of health care services.
13,58,59
The Nordic
countries have also had a long standing tradition of maintaining
birth registers, as early as the 1950s in some countries,
60,61
and
this has allowed for broader application of linkage techniques in
perinatal health research. Longer follow-up time broadens the
scope of potential research questions and enables studies across
generations.
The reasons for linkage are related to the organization of the
health and data collection systems and these vary across countries.
For example, in the Netherlands, midwives, general practitioners,
obstetricians and neonatologist have separate databases which are
linked to bring together perinatal care data for women who have
been client of more than one profession,
62
but other countries do
not need to do this. Another example relates to cause of death
recording: in the UK causes of death are recorded on stillbirth and
death certificates, while in France linkage is necessary to access this
information because civil registration of deaths is distinct from the
medical certification of the causes.
7
Capacity for linkage also depends on the availability of matching
variables. Whereas many national registers in Europe anonymize
their records, others countries and in particular the Nordic
countries make universal identification numbers available in all
their routine databases.
8
Universal identifiers facilitate linkage
between statistical, administrative and health authorities, although
in the absence of identifying variables probabilistic techniques can be
used.
63
In the Netherlands, validation of the probabilistic approach
applied to the Dutch Perinatal registers yielded less than 1% error.
62
There are multiple obstacles associated with linkage including
cultural, organizational, structural, legal and technical issues.
Specific obstacles identified in research on linkage include high
costs, lack of software compatibility, need for additional statistical
training, poor access to electronic records, missing data or varying
interpretations of data privacy frameworks across organizations.
64–66
Data systems are also often managed by different institutions and
communication and identification of common goals may hamper
efforts to merge data sources. Moreover, concerns over privacy
and the biases introduced when linkages are incomplete may
influence countries’ willingness to institute routine linkage.
Further research is needed to explore these obstacles, particularly
how they have been overcome in countries that have instituted
routine linkage, and their relative weight in countries where
linkage is underdeveloped.
Our results underscore the multiple ways that record linkage can
improve capacity for high quality perinatal health surveillance. First
of all, data from the methods studies in the literature review
showed that linkage can be used for validation and to ascertain
new perinatal data items and outcomes.
62,65,67,68
In France for
instance, linkage of the deaths of women of childbearing age to
birth records and hospital discharge data makes it possible to
account for all maternal deaths and reduce underreporting.
7
Further, by linking birth certificate data on gestational age and
birth weight with death certificates it is possible to calculate
subgroup mortality rates which are essential for monitoring infant
health status and understanding patterns of mortality over
time.
3,6,65,69,70
Because vital statistics data are available everywhere
in Europe,
1
basic linkage of birth and death certificates should be
possible in all countries. All European countries also have hospital
discharge data,
71
yet routine linkage of these data with birth certifi-
cates and other population datasets was only carried out in only a
fourth of countries.
Data on hospitalizations contain valuable information about
clinical procedures and diagnoses because their primary use is for
management and financing.
6
Basic socioeconomic characteristics are
rarely included in hospital data, but these can be retrieved from
other data sources, such as census data or registers on education,
occupation and income. Birth certificate data in most countries
provide information on characteristics such as place of birth, place
of residence, marital status or occupation. Hence, linkage between
hospital discharge data and population-based registers can be used
to assess the burden of health disparities across socio-economic
groups.
72–74
The additional variables acquired through linkage
allow for more refined and expanded analyses of trends and
patterns in key perinatal indicators.
67,69,75–82
Record linkage also enables the surveillance of specific clinical
subgroups such as infants born with congenital anomalies or from
ART. Whereas only two countries, Finland and Malta, conduct
routine linkages with their congenital anomaly registers, these
types of linkages were frequent in the literature. In about 15% of
studies, researchers focused on the impact of ART as well as on the
effects of teratogens and prescription drugs on congenital anomalies.
For example, two US studies looked at exposure to anesthetic gases
and congenital anomalies in offspring of female registered nurses
83
and the association between maternal exposure to ambient air
pollution and congenital heart disease.
84
More generally, our review shows that linkage of routine data
systems is a valuable tool for research which can provide insight
into maternal and infant health indicators but also into the
etiology, prognosis and consequences of conditions such as Legg
Calves Perthes disease, cerebral palsy, or multiple sclerosis.
Linkage of routine systems also facilitates life-course research on
the long term outcomes of mothers and their newborns. Half of
the studies in our review were longitudinal. A cohort, e.g. of all
women of reproductive age, can be identified and monitored by
linking data relating to these women from multiple data sources
thereby increasing the power of statistical analyses without having
to incur the costs of a long follow-up time.
This systematic review builds on a large number of studies linking
routine databases on perinatal health. We also identified countries in
which linkage is currently undertaken for routine perinatal health
monitoring to get information about the linkages put in place and to
permit other countries to benefit from their experience. In countries
where specific data sets are linked regularly, as in the Nordic
countries, authors did not always explicitly mention ‘linkage’ in
the abstracts. This could have led to an under-estimation of the
number of perinatal health studies published during our review
period. We only included studies in referenced databases and thus
did not include studies published on statistical institution’s websites
only or other types of grey literature such as agency health and policy
reports. Also, countries differed in the terminologies they used for
their data sources, especially when translating them into English and
this can make it difficult to distinguish between e.g. a morbidity
database, hospital records and a birth register.
Data linkage increases the availability of data for surveillance and
assessment of differences across countries and over time. Linkage
Linking databases on perinatal health 5of9
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techniques can also contribute to the generation of knowledge about
the causes and consequences of ill health. More specifically, linkage
of data from birth and death certificates provides more and higher
quality information about mortality and should be prioritized in
countries where these sources are not yet linked. Linking hospital
discharge data and civil registration data should also be a priority as
it increases the amount of information available about each birth
and can be used to double check the completeness of registration of
births and deaths in hospital databases. Finally, linkage makes it
possible to augment commonly available birth data with informa-
tion on specific outcomes or exposures in relation to health and
well-being across the life course. These linkages will depend on
other existing databases (i.e. congenital anomalies registers, pharma-
ceutical databases) and the use of linkage for surveillance and
research in other health areas and sectors such as education,
employment or housing.
In conclusion, some countries integrate data linkage into their
routine perinatal health surveillance systems and make these data
available for research, but this is not a universal practice throughout
Europe. Current discussion at the EU-level and across Member
States includes moving towards the establishment of a
European health information system, and strengthening health
reporting mechanisms.
85,86
Linking data on perinatal health is a
feasible and readily available option for improving the quality and
completeness of health indicators thereby adding value to existing
national and international investment in health information. Further
research is needed on the obstacles to linkage in countries which do
not practice it routinely. Promoting these recommendations about
the linkages which are most useful for perinatal health reporting and
broader adoption of linkage could yield substantial gains for
research and surveillance of perinatal health nationally and
internationally.
Supplementary data
Supplementary data are available at EURPUB online.
Acknowledgements
The member of the The Euro-Peristat Scientific Committee include:
Gerald Haidinger (Austria), Sophie Alexander (Belgium), Pavlos
Pavlou (Cyprus), Petr Velebil (Czech Republic), Laust Mortensen
(Denmark), Luule Sakkeus (Estonia), Mika Gissler (Finland),
Be
´atrice Blondel (France), Nicholas Lack (Germany), Aris
Antsaklis (Greece), Istva
´n Berbik (Hungary), Helga So
´lO
´lafsdo
´ttir
(Iceland), Sheelagh Bonham (Ireland), Marina Cuttini (Italy), Janis
Misins (Latvia), Jone Jaselioniene (Lithuania), Yolande Wagener
(Luxembourg), Miriam Gatt (Malta), Jan Nijhuis (Netherlands),
Kari Klungsøyr (Norway), Katarzyna Szamotulska (Poland),
Henrique Barros (Portugal), Mihai Horga (Romania), Jan Cap
(Slovakia), Z
ˇiva Novak Antolic
ˇ(Slovenia), Francisco Bolu
´mar
(Spain), Karin Gottvall (Sweden), Sylvie Berrut (Switzerland),
Alison Macfarlane (United Kingdom). Project coordination:
Jennifer Zeitlin, Marie Delnord, Ashna Hindori-Mohangoo.
The authors acknowledge the following contributors to the
European Perinatal Health Report: Health and Care of Pregnant
Women and Babies in Europe in 2010:
Austria, Gerald Haidinger, The Medical University of Vienna,
Department of Epidemiology, Centre of Public Health; Jeannette
Klimont, Statistics Austria; Belgium, Sophie Alexander, Wei-Hong
Zhang, Miche
`le Dramaix-Wilmet, Me
´lissa Van Humbeeck,
Universite
´Libre de Bruxelles, School of Public Health,
Epidemiology, Biostatistics and Clinical Research Centre; Charlotte
Leroy, Anne-Fre
´de
´rique Minsart, Virginie van Leeuw, Centre
d’Epide
´miologie Pe
´rinatale (Cepip); Evelyne Martens, SPE (Study
Center for Perinatal Epidemiology); Myriam De Spiegelaere,
Brussels Health and Social Observatory, Freddy Verkruyssen,
Michel Willems, FPS Economy, SMEs, Self-employed and Energy;
Willem Aelvoet, The Federal Public Service (FPS) Health, Food
Chain Safety and Environment; Jean Tafforeau, Francoise Renard,
Denise Walckiers, Focal Point for the data collection on national
health statistics for Eurostat, OECD and WHO; Deborah Cuignet,
Philippe Demoulin, French Community of Belgium; Heidi Cloots,
Erik Hendrickx, Anne Kongs, Flemish Agency for Care and Health;
Cyprus, Pavlos Pavlou, Despina Stylianou, Theopisti Kyprianou,
Ministry of Health, Health Monitoring Unit; Nicos Skordes,
Pediatric Department, Makarios III Hospital; Czech Republic, Petr
Velebil, Institute for the Care of Mother and Child; Denmark, Jens
Langhoff Roos, Obstetrics Clinic, Rigshospitalet, Copenhagen
University; Anne-Marie Nybo Anderson, Laust Hvas Mortensen,
University of Copenhagen; Estonia, Luule Sakkeus, Estonian
Institute for Population Studies, Tallinn University; Finland, Mika
Gissler, Anna Heino, Annukka Ritvanen, THL National Institute for
Health and Welfare; France,Be
´atrice Blondel, Marie-He
´le
`ne Bouvier
Colle, Marie Delnord, Jennifer Zeitlin, National Institute of Health
and Medical Research (INSERM) U1153; Anne Ego, RHEOP
Register for Disabled Children and Perinatal Observatory; Gre
´goire
Rey, National Center of Statistics for Medical Causes of Death
(Ce
´piDc), National Institute of Health and Medical Research
(INSERM); Germany, Nicholas Lack, Bavarian Institute for
Quality Assurance; Guenther Heller, AQUA-Institut; Anton Scharl,
Department of Obstetrics and Gynaecology; Klinikum Amberg;
Greece, Aris Antsaklis, Peter Drakakis, Athens University Medical
School, Athens; Hungary, Istva
´n Berbik, Department of Obstetrics
and Gynaecology, Vaszary Kolos Teaching Hospital; Iceland, Helga
So
´lO
´lafsdo
´ttir, Ragnheiôur I. Bjarnadottir, Hildur Harôardo
´ttir,
Brynja Ragnarsdo
´ttir, Vigdı
´s Stefa
´nsdo
´ttir Landspitali University
Hospital; Sigrı
´ôur Haraldsdo
´ttir, Landlaeknis Directorate of
Health; Ireland, Sheelagh Bonham, Aisling Mulligan, The
Healthcare Pricing Office (HPO); Italy, Marina Cuttini, Pediatric
Hospital of Baby Jesus, Unit of Epidemiology; Cristina Tamburini,
Rosaria Boldrini, General Directorate for the Health Information
and Statistical System, Italian Ministry of Health; Sabrina Prati,
Marzia Loghi, Cinzia Castagnaro, Stefano Marchetti, Alessandra
Burgio, Central Directorate for Socio-demographic and
Environmental Statistics, Italian National Institute for Statistics-
ISTAT; Monica Da Fre
`, Epidemiology Observatory, Regional
Agency for Health of Tuscany Latvia, Janis Misins, Irisa Zile, The
Centre for Disease Prevention and Control of Latvia; Lithuania,
Jelena Isakova, Rita Gaidelyte, Jone Jaselione, Institute of Hygiene,
Health information centre; Luxembourg, Yolande Wagener, Guy
Weber Ministry of Health, Department of Health, Division of
Preventive and Social Medicine; Audrey Billy, Aline Touvrey-
Lecomte, Public Health Research Center; Malta, Miriam Gatt,
Dept of Health Information and Research, National, Obstetric
Information Systems (NOIS) Register; Netherlands, Jan Nijhuis,
Maastricht University Medical Center, Department of Obstetrics &
Gynecology, Maastricht; Karin van der Pal –de Bruin and Ashna
Hindori- Mohangoo, TNO Healthy Living, Department Child
Health, Leiden; Peter Achterberg, National Institute for Public
Health and the Environment; Chantal Hukkelhoven and Ger de
Winter, The Netherlands Perinatal Registry; Anita Ravelli,
Academic Medical Research Center; Greta Rijninks-van Driel, The
Royal Dutch College of Midwives; Pieter Tamminga, Paediatric
Association of the Netherlands; Martin Groesz, Perinatal Audit
Netherlands; Patsy Elferink-Stinkens, Statistics Netherlands;
Norway, Kari Klungsoyr, Medical Birth Registry of Norway,
Norwegian Institute of Public Health and Department of Global
Public Health and Primary Care, University of Bergen; Arild Osen,
Marta Ebbing, Medical Birth Registry of Norway, The Norwegian
Institute of Public Health; Poland, Katarzyna Szamotulska, National
Research Institute of Mother and Child, Department of
Epidemiology and Biostatistics with collaboration from The
Central Statistical Office, the National Health Fund and Ministry
of Health; Portugal, Henrique Barros, Sofia Correia, University of
6of9 European Journal of Public Health
by guest on January 15, 2016http://eurpub.oxfordjournals.org/Downloaded from
Porto Medical School, Department of Clinical Epidemiology,
Predictive Medicine and Public Health; Institute of Public Health;
Romania, Mihai Horga, Senior Advisor at the East European
Institute for Reproductive Health, East European Institute for
Reproductive Health; Alexandra Cucu, National Institute of
Public Health; Slovakia, Jan Cap, National Health Information
Center; Slovenia,Z
ˇiva Novak-Antolic
ˇ, University Medical Centre,
Perinatology Unit, Ljubljana University; Ivan Verdenik, University
Medical Centre, Department of Obstetrics& Gynecology, Research
Unit; Spain, Francisco Bolumar, Alcala University Medical School;
Mireia Jane
´, Maria Jose
´Vidal, Public Health Surveillance Direction,
Catalan Public Health Agency; Carmen Barona, Rosa Mas, Public
Health, Generalitat Valenciana; Adela Recio Alcaide,
National Institute for Statistics (INE); Sweden, Karin Gottvall,
Ellen Lundqvist, The National Board of Health and Welfare,
Department of Statistics, Monitoring and Evaluation, Statistics on
Public Health and Social Care Unit; Switzerland, Sylvie Berrut,
Swiss Federal Statistical Office, Section Health; Claudia Ko
¨nig,
Monika Schmid, Institut fu
¨r Hebammen, ZHAW Zu
¨rcher,
Hochschule fu
¨r Angewandet Wissenschaften; United Kingdom,
Alison Macfarlane, Nirupa Dattani, City University London; Jim
Chalmers (now retired), Kirsten Monteath, Information
Services Division, NHS National Services Scotland; Marie Climson,
National Records of Scotland; Leslie Marr, Healthcare Improvement
Scotland; Rod Gibson, Birthchoice UK; Gwyneth Thomas,
Rhian Osborne, Health Statistics and Analysis Unit, Welsh
Government; Russell Brown, NHS Wales Informatics Service;
David Sweet, Joanne Evans, Office for National Statistics;
Sinead Magill, Adele Graham, Heather Reid, Public Health
Agency; Terry Falconer, Karen McConnell, Northern Ireland
Maternal and Child Health, Public Health Agency (now retired);
Neil McComb, Human Fertilisation and Embryology Authority.
Funding
This study was funded by grants from the European Commission for
the Euro-Peristat project: 2010 13 01 and for the Bridge Health
project: 664691. The funding agency was not involved in the
study. This study used aggregated national indicators, ethical
approval was not required.
Conflicts of interest: None declared.
Key points
Record linkage has been successfully used for research on
maternal, fetal and infant health risk factors and outcomes,
although this research is concentrated in only a few
countries.
That linkages are not systematic practice for perinatal health
surveillance could explain gaps in data availability in the
European Perinatal Health Report 2010 and limitations in
countries’ capacity to collect data for key subgroup
populations.
Linking data on perinatal health is a feasible and readily
available option for improving the quality and completeness
of health indicators thereby adding value to existing national
and international investments in health information
systems.
Having common recommendations in the EU about which
linkages are most useful for perinatal health reporting and
broader adoption of linkage could yield substantial gains for
research and surveillance of perinatal health nationally and
internationally.
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