1. Methodology background


 National Statistic   
 Frequency  Quarterly and annual
 How compiled  Based on third party data
 Geographic coverage  England and Wales
 Last revised  22 March 2017

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2. Executive summary

Conception statistics are estimates which bring together records of birth registrations collected under the Births and Deaths Registration Act (1953) and of abortions under the Abortion Act (1967), amended by the Human Fertilisation and Embryology Act (2008). They include all the pregnancies of women usually resident in England and Wales which lead to one of the following outcomes:

  • a maternity at which 1 or more live births or stillbirths occur, which is registered in England and Wales
  • a termination of a pregnancy by abortion under the 1967 Act, which took place in England and Wales

Miscarriages and illegal abortions are not included in the statistics. Maternities which result in 1 or more live births or stillbirths are counted once only.

The annual Conception statistics publication consists of a number of data tables accompanied by a statistical bulletin. The tables released show the latest year’s figures with some tables also showing historical data for comparison. The User guide to conception statistics provides further information on data quality, legislation and procedures relating to conception statistics.

To meet user needs, timely but Provisional quarterly conceptions to women aged under 18 are published by area of usual residence. Quarterly conception rates and rolling annual rates are also provided where area of usual residence is within England.

This document contains the following sections:

  • Output quality

  • About the output

  • How the output is created

  • Validation and quality assurance

  • Coherence and comparability

  • Concepts and definitions

  • Other information, relating to quality trade-offs and user needs

  • Sources for further information or advice

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3. Output quality

This document provides a range of information that describes the quality of the data and details any points that should be noted when using the output.

We have developed Guidelines for measuring statistical quality based on the 5 European Statistical System (ESS) Quality Dimensions. This document addresses these quality dimensions and other important quality characteristics, which are:

  • relevance
  • timeliness and punctuality
  • accuracy
  • coherence and comparability
  • output quality trade-offs
  • assessment of user needs and perceptions
  • accessibility and clarity

More information is provided about these quality dimensions in the sections below.

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4. About the output

Relevance

(The degree to which statistical outputs meet users’ needs.)

Throughout the year Provisional quarterly conceptions to women aged under 18 are released on our website. The release provides numbers of conceptions and conception rates (English areas only) for women aged under 18 by area of usual residence (counties, unitary authorities and metropolitan county districts), England and Wales, by quarter of conception. Quarterly conception rates and rolling annual conception rates are published. The rolling annual rates are calculated using the last 4 quarters’ conception numbers and the populations used are mid-year population estimates from the corresponding years weighted accordingly.

Annual Conception statistics are published by age of woman at conception, marital/civil partnership status at time of conception and outcome (maternity or abortion). Conception statistics for local authorities are published for women aged under 16, under 18 and all ages.

An animated map of conceptions in England and Wales allows trends in under 18 conception rates since 1998 to be analysed more easily at the local area level.

Conception statistics do not include:

  • conceptions leading to a maternity for women usually resident in England and Wales who give birth abroad
  • conceptions leading to a maternity for women whose usual residence is outside England and Wales where the birth took place within England and Wales
  • abortions to women whose usual residence is outside England and Wales
  • miscarriages or illegal abortions (more information is available in the Accuracy section)

Following the implementation of the Human Fertilisation and Embryology Act (2008), same-sex female couples have been able to register the birth of a child as mother and second parent since 1 September 2009. Abortion notifications also contain information about whether the woman was in a civil partnership or marriage with a female partner.

Due to the relatively small numbers of conceptions to same-sex couples, conceptions to same sex couples who are married or in a civil partnership are included with conceptions within marriage, while conceptions to same-sex couples not in a marriage or civil partnership are included with conceptions outside marriage. The number of conceptions to same-sex couples is footnoted on relevant tables to assist users. Given the relatively small numbers of conceptions to same-sex couples the impact on statistics is negligible.

Conception figures are covered by the disclosure control protocol for abortion statistics. In June 2015 this protocol was revised. The requirement to suppress counts and rates is determined by the number of women in the underlying population. Full details can be found in the Disclosure control protocol for abortion statistics. Occasionally it is necessary to apply secondary suppression to avoid the possibility of disclosure by differencing. Prior to June 2015, for conceptions leading to abortions, counts less than 10 and rates based on fewer than 10 events were suppressed. To protect the confidentiality of conceptions data, all counts lower than 5, and all rates based on fewer than 5 events were also suppressed.

The Department of Health (DH) leads for the Government on reducing under 18 conceptions and is a key user of conception statistics. DH monitors the rate of under 18 conceptions under the Public Health Outcomes Framework 2013 to 2016 as part of the measures of health improvement. DH uses the numbers of conceptions at all ages as a marker for the success of policies on access to contraception (and other sexual health services). DH uses conception statistics by age because they are of use to maternity service providers, particularly during the antenatal period, to allow them to plan for the level of demand for antenatal services.

Public Health England (PHE) is a key user of conception statistics. PHE have a role in providing information and evidence to local areas, as well providing more tailored advice and support. Conceptions data, information, tools and resources (including policy, practice and research) are brought together in a single knowledge hub for use by local decision makers.

In Wales, teenage conception rates are used widely as outcome indicators in Sexual Health and Well-being Action Plan for Wales, 2016 to 2019, as well as being a general indicator of health and health inequality for example in Our healthy future. The conception rate for under 18 years is the most commonly used with the underage rate (under 16 years) being a key health indicator for children and young people.

Local authorities use the data, particularly the number and rate of under 18 conceptions to feed into their Joint Strategic Needs Assessments and to inform their commissioning decisions. They also use the statistics to make comparisons with other local areas, the county, region and also country.

Sexual health charities which provide the public with information, advice and support services use the statistics to promote services that contribute to the reduction in conceptions.

Timeliness and punctuality

(Timeliness refers to the lapse of time between publication and the period to which the data refer. Punctuality refers to the gap between planned and actual publication dates.)

The release of each conceptions publication is announced via the GOV.UK release calendar at least 4 weeks before publication.

Maternities are compiled using information collected at birth registration and therefore, births need to be registered before they can be used to compile conception statistics. Consequently, conceptions data cannot be processed until births that were conceived on the last applicable day of the quarter/year have had time to be legally registered (within 42 days of the birth). We then require 3 months to quality assure the data and compile conception statistics. Provisional quarterly conception statistics are therefore published 14 months after the end of the data quarter in which the conception occurred.

Prior to the 2009 data year (published in 2011), annual data were released twice a year: provisional annual Conception statistics were released in February (14 months after the end of the data year) followed by a final annual release in the Annual Reference Volume Conception statistics, published in the autumn (around 22 months after the end of the data year). The tables published in the provisional release differed from those published in the final release.

We consulted users of conception statistics between 22 February and 19 April 2011. This Review of conception statistics sought the views of users on proposed changes to conception outputs. One aim of these proposals was to reduce the cost of producing conception statistics by publishing figures once a year (around February), rather than twice a year. In addition, we proposed a core set of tables for future publications. Users were asked to comment on these and other proposed changes. We also consulted directly with main government customers on the proposals. The majority of users supported the proposal to move to 1 annual publication of conception statistics since there was no significant impact on data quality. Consequently, since 2011 (2009 data year) only 1 release of annual conception statistics has taken place with figures being published 14 months after the end of the data year.

Final annual conception statistics for 2000 and earlier years were included in Birth statistics (series FM1). The last edition of Series FM1 was published in December 2009.

Publication of quarterly data has only been delayed on 1 occasion. Figures for June quarter 2002 figures were affected by the late supply of abortion data from the Department of Health following the transfer of processing work to them by ONS.

For more details on related releases, the GOV.UK release calendar is available online and provides 12 months’ advance notice of release dates. In the unlikely event of a change to the pre-announced release schedule, public attention will be drawn to the change and the reasons for the change will be explained fully at the same time, as set out in the Code of Practice for Official Statistics.

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5. How the output is created

Conceptions are maternities (the number of pregnant women who give birth) plus abortions and this information is obtained from administrative sources. Maternities data are derived from information recorded at birth registration, a service carried out by the General Register Office. Abortion data comes from DH and is based on abortion notifications provided by abortion clinics.

The User guide to conception statistics includes more information detailing methodology of production.

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6. Validation and quality assurance

Accuracy

(The degree of closeness between an estimate and the true value.)

Conception statistics are estimates derived by combining numbers of maternities and abortions.

Maternities data are derived from information recorded at birth registration, a service carried out by the General Register Office. These data represent the legal record under the Births and Deaths Registration Act (1953), making it the best and most complete data source. The information is normally supplied by the parent(s).

Birth registrations are then linked to the birth notification (completed by the midwife or doctor in attendance at the birth) in order to obtain mother’s date of birth when it has not been recorded at birth registration. Details on data processing and quality checks for birth registrations can be found in the Quality and methodology information for births and User guide to birth statistics.

Abortion data is supplied by the Department of Health and is based on abortion notifications provided by abortion clinics. These data represent the legal record under the Abortion Act (1967), making it the best and most complete data source.

Abortion notifications go through an agreed series of checks and values for missing items are imputed at DH before being supplied to us, this ensures data are of sufficient quality. Each quarter there are also updates on previous quarters which have not been previously finalised; these updates will contain records where DH raised queries which have been resolved.

During 2013 the number of Ground E HSA4 notifications (“substantial risk” that the child might be born “seriously handicapped”) was found to be lower than the number reported to the congenital anomaly registries. DH has worked closely with the National Down’s Syndrome Cytogenetic Register (NDSCR) to explore this discrepancy and make recommendations. Results suggested that an abortion notification was made for about 54% of NDSCR records. Hence, there is potentially an undercount of Ground E abortions. Between 2011 and 2013, there has been a 17.8% increase in the submission of abortion notifications for Down’s syndrome. DH continues to work closely with the Royal College of Obstetricians and Gynaecologists (RCOG) and other organisations in implementing the recommendations where possible.

Conception statistics do not include miscarriages or illegal abortions. NHS Choices estimate that 1 in 5 confirmed pregnancies will end in miscarriage. It is impossible to determine the extent of illegal abortions, for example, by women using drugs bought from the Internet. The only statistics available are where complications arise from illegal abortions resulting in illness or death. In 1965, before abortion was legalised, the number of women discharged from hospital with post-abortion sepsis (Col 202) was 3,050; in 1982 it was 390. Why Mothers Die 2000-2002: The Sixth Report of the Confidential Enquiries into Maternal Deaths in the UK found that in the 3 years from 1961 to 1963, 139 women were recorded as dying as a result of abortions. Saving Mothers’ Lives: reviewing maternal deaths to make motherhood safer 2006-2008 reported no deaths from abortions from 2006 to 2008. Given the steady rise in numbers of legal abortions since 1968, and the improvements in access to abortion it can be assumed that the vast majority of abortions carried out in England and Wales today are legal ones.

Information on the exact date of conception cannot be obtained from the birth registration or abortion notification, so formulae are used to estimate the date based on whether the conception resulted in a live birth, stillbirth or abortion. The formulae are published in our User guide to conception statistics.

In any year it is possible for a woman to appear more than once in conception statistics as it is possible for her to:

i) have multiple abortions

ii) conceive twice where both conceptions lead to a maternity

iii) have multiple conceptions which result in a maternity and 1 or more abortions

iv) have an abortion and a birth as part of her pregnancy when carrying more than 1 child

Following the Review of conception statistics between February and April 2011, we publish annual figures only once a year in February/March. This change reduces the cost of producing conception statistics and has negligible impact on data quality given the improved accuracy of provisional conception figures (in 2008 there was generally less than 0.1% difference in the number of conceptions within each age group in England and Wales). The main reasons for the improved accuracy were:

  • reductions in the percentage of birth registrations where mother’s date of birth was not stated

  • moves within ONS to conduct more timely quality checks on birth registrations

  • daily receipt of birth registrations through the Registration Online system (RON)

At the time that annual conception statistics are now compiled, only the births annual subset for the earlier year (relating to maternities which occurred in the same year as the conception) will have been finalised. However, the births quarterly subsets for the subsequent year which are required for the annual conceptions release will have gone through full quality assurance.

Prior to the 2010 data year for conception statistics, differences between provisional and final figures resulted from:

i) maternity records where mother’s date of birth was missing at registration had the age of mother at conception imputed for the final annual release. In the provisional release, age of mother had only been imputed for maternities occurring in the same calendar year as the conception. Hence in provisional conception figures, if the age of the mother was missing, for maternities occurring in the subsequent calendar year to the conception, the conception was included in the total count, but excluded from any age breakdown (imputation routines were only run on final annual births datasets and hence had not yet been applied to these maternities)

ii) abortion records which needed to be clarified with clinics and were unresolved were excluded from the provisional annual releases but included in the finalised dataset following clarification

Coherence and comparability

(Coherence is the degree to which data that are derived from different sources or methods, but refer to the same topic, are similar. Comparability is the degree to which data can be compared over time and domain for example, geographic level.)

Conception statistics are not directly comparable with birth statistics for the following reasons:

  • conception statistics include abortions

  • conception statistics are published by date of conception while birth statistics are published by date of birth so the time periods are not comparable

  • conception statistics do not count multiple births by the same woman as they are derived using maternities (the number of women giving birth rather than the number of babies born)

The Department of Health publishes annual Abortion statistics by age of woman, number of previous abortions, length of gestation, source of funding, health area of usual residence of woman, method of abortion, ethnicity of woman and grounds for abortion.

Abortion data used in conception statistics are not directly comparable with abortion statistics published by the Department of Health (DH). This is because DH abortion statistics are published by date of abortion whereas we use abortion data based on the date of conception. Some abortions will relate to conceptions which occurred in the previous calendar year.

Conception statistics in Scotland are available for women aged under 16, under 18 and under 20. They have been produced to a revised methodology since 2007 to become more comparable to those in England and Wales. Prior to this, they included therapeutic miscarriages which required a hospital stay and were based on financial years rather than calendar years. More information on the differences in methodology which existed previously can be found on the ISD Scotland website.

In Northern Ireland it is lawful to perform an operation for the termination of a pregnancy, where:

  • it is necessary to preserve the life of the woman

  • there is a risk of real and serious adverse effect on her physical or mental health, which is either long term or permanent

In any other circumstance it would be unlawful to perform such an operation. Due to the small numbers of abortions carried out in Northern Ireland each year, and in order to protect patient confidentiality, information on terminations of pregnancy is only released at Northern Ireland and Health and Social Care Trust level. Further information on the number of terminations of pregnancy carried out in Northern Ireland can be found on the Department of Health, Social Services and Public Safety’s website.

There are no comparable statistics internationally due to the lack of abortion statistics.

The conception rate provides a standard measure (that is the number of conceptions per thousand women in the age group) which can be used to make comparisons over time and between different areas. This measure takes account of the size of the population. The overall rate for all ages is not standardised and so does not take into account the age structure of the population. Age-specific rates enable easy comparisons between different age groups. Rates for areas with a low population should be treated with caution since a small change in the number of conceptions can lead to a large change in the rate. In these areas rates should be assessed alongside numbers of conceptions and statistics over several years should be taken into consideration.

Time series data are available going back to 1969. However, there are issues of comparability due to changes in the way we estimated the age at conception in 1999. A back series of data to 1987 was produced. Details of change are available in the 1998 Birth statistics (series FM1). Changes in 1992 to the stillbirth definition (see below) will also affect comparability over time.

The Stillbirth Definition Act (1992) defines a stillbirth from being “any child that has issued forth from its mother after the 24th week of pregnancy, and that did not at any time after being completely expelled from its mother breathe or show any signs of life”. Previously, the definition of a stillbirth was as above, but for 28 or more weeks of gestation. For this reason conception statistics from 1993 are therefore not fully comparable with those for previous years.

Conception rates for 2002 to 2008 were revised in the 2010 annual conceptions release in time series tables following revisions to the mid-year population estimates for those years. The revisions were footnoted on tables and in the accompanying metadata.

Conception rates for 2002 to 2010 for England and Wales were revised again in the 2011 annual conceptions release following further revisions to population estimates to take account of the 2011 Census. Conceptions rates for 2002 to 2010 for subnational areas were also recalculated following the publication of revised subnational population estimates on 30 April 2013. The revisions were footnoted.

Conceptions outputs are produced to geographical boundaries in place during the year the conception occurred. This approach means that changes in boundary can affect the comparability of statistics over time.

Following the move to publish only 1 set of annual conception statistics from 2011 onwards (instead of publishing a provisional and then final release), several users expressed concerns over the comparability of pre-2008 figures (published 22 months after the end of the data year) and post 2008 figures (published 14 months after the end of the data year). Analysis shows that these figures do represent a comparable time series given the improvements in the accuracy of annual conception figures published 14 months after the end of the data year.

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7. Concepts and definitions

(Concepts and definitions describe the legislation governing the output and a description of the classifications used in the output.)

Information on UK legislation relating to conception statistics and definitions of terms are included in the User guide to conception statistics and the User guide to birth statistics.

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8. Other information

Output quality trade-offs

(Trade-offs are the extent to which different dimensions of quality are balanced against each other.)

Following the Review of conception statistics in 2011, it was agreed with users that there would be a single release of annual conceptions data (rather than a provisional and final release) as the difference between provisional and final conceptions estimates was relatively small. In 2008, there was generally less than 0.1% difference in the number of conceptions within each age group in England and Wales. This change has negligible impact on the accuracy of conception statistics but greatly reduces the cost of producing the statistics.

Maternities data included in Conception Statistics have been derived from the births database. Where the mother’s date of birth was not stated at registration it is obtained from the corresponding birth notification record. Where this is not possible, the age of mother is imputed. More information on the imputation method can be found in section 1.3 of the User guide to birth statistics.

Conception statistics for 2009 by age exclude maternities where the mother’s age was not recorded and the birth occurred in 2010. For the 2009 data year, final conception statistics were released before the 2010 annual births dataset had age of mother imputed.

From 2010 conceptions data onwards, where a missing age of mother could not be obtained from the corresponding birth notification, age of mother was imputed by drawing the age from a complete record with similar characteristics to the incomplete record. The percentage of records where age of mother remains missing following birth notification matching is very small, imputation ensures that the risk of non-response bias in published outputs is minimal. The impact on comparability of statistics over time and between areas is also minimal.

Assessment of user needs and perceptions

(The processes for finding out about uses and users, and their views on the statistical products.)

We welcome feedback on the content, format and relevance of our releases and encourage users to send feedback to vsob@ons.gsi.gov.uk.

Feedback is requested with all e-mails sent by customer services teams within Vital Statistics Outputs Branch.

Feedback is also received through our regular attendance at user group meetings and conferences.

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9. Sources for further information or advice

Accessibility and clarity

(Accessibility is the ease with which users are able to access the data, also reflecting the format in which the data are available and the availability of supporting information. Clarity refers to the quality and sufficiency of the release details, illustrations and accompanying advice.)

Our recommended format for accessible content is a combination of HTML webpages for narrative, charts and graphs, with data being provided in usable formats such as CSV and Excel. Our website also offers users the option to download the narrative in PDF format. In some instances other software may be used, or may be available on request. Available formats for content published on our website but not produced by us, or referenced by our website but stored elsewhere, may vary. For further information please contact vsob@ons.gsi.gov.uk.

For information regarding conditions of access to data, please refer to the links below:

Special extracts and tabulations of divorces data for England and Wales are available to order (subject to legal frameworks, disclosure control, resources and our charging policy, where appropriate). Enquiries should be made to Vital Statistics Outputs Branch (vsob@ons.gsi.gov.uk or telephone: +44 (0)1329 444110). User requested data will be published onto our website.

Useful links

Provisional quarterly conceptions to women aged under 18 are published by area of usual residence. The quarterly conception rate and rolling annual conception rates are provided where area of usual residence is within England.

Annual Conception statistics are published by age of woman at conception, marital or civil partnership status at time of conception and outcome (maternity or abortion). Conception statistics for local authorities are published for women aged under 16, under 18 and all ages.

An animated map of conceptions in England and Wales allows trends in under 18 conception rates since 1998 to be analysed more easily at the local area level.

The User guide to conception statistics has more information on data quality, legislation and procedures relating to conception statistics.

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