1. Introduction

We produce infant mortality statistics that are published under the National Statistics logo, the designation guaranteeing that those outputs have been produced to high professional standards set out in the Code of Practice for Official Statistics and have been produced free from any political interference.

This page provides information on the collection, production and quality of mortality data for:

The Child Mortality Statistics Quality and Methodology Information document contains important information on:

  • the strengths and limitations of the data
  • the quality of the output: including the accuracy of the data and how it compares with related data
  • uses and users
  • how the output was created

The User guide to birth statistics provides information on the collection, production and quality of birth statistics based on birth registration data.

Child mortality statistics and Birth cohort tables for infant deaths replaced the annual reference volume Mortality statistics: childhood, infant and perinatal (DH3) in 2010. The current releases contain selected tables from DH3, although some tables have been amended to improve presentation.

The ONS policy on protecting confidentiality in birth and death statistics (currently under revision) is available on our website.

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2. Occurrences and registrations

Deaths

The annual total of deaths occurring in a calendar year is taken from the standard dataset for death occurrences created from the deaths database. To be acceptably complete, this annual extract must be taken some months after the end of the data year to allow for late death registrations. Although there will inevitably be a small number of deaths not registered when the annual extract of death occurrences is taken, delaying the timing of the extract any further will delay the publication of the data.

The Birth cohort tables for infant deaths represent those babies born in a calendar year who died before their first birthday.

Births

The annual totals of live births and stillbirths are derived from the standard annual extract of live births and stillbirths. This extract includes all births occurring and registered in a calendar year plus late registrations from the previous year.

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3. Childhood and infant deaths

In Child mortality statistics, childhood deaths are defined as between 1 and 15 years of age. Infant deaths (under 1 year) at various ages are defined as:

  • early neonatal – deaths under 7 days
  • perinatal – stillbirths and early neonatal deaths
  • late neonatal – deaths between 7 and 27 days
  • neonatal – deaths under 28 days
  • postneonatal – deaths between 28 days and 1 year

3.1 Stillbirths

The Stillbirth (Definition) Act 1992 defines a stillbirth as:

“a child which has issued forth from its mother after the twenty-fourth week of pregnancy, and which did not at any time after becoming completely expelled from its mother breathe or show other signs of life”.

This definition has been in use since 1 October 1992. Prior to this, the Births and Deaths Registration Act 1953 defined a stillbirth as above, but at 28 or more weeks completed gestation. Figures for stillbirths from 1993 are thus not comparable with those for previous years. The effect of this change on figures for 1992 is analysed in the annual volume of birth statistics for that year (OPCS 1994).

3.2 Registration and certification of stillbirths, neonatal and infant deaths

General information about the registration and certification of stillbirths, neonatal and infant deaths in England and Wales can be found in the User guide to mortality statistics. It also provides information about the specific details collected when a death is certified and registered.

3.3 Death rates

The rates presented in this publication are:

  • stillbirth rate: number of stillbirths, per 1,000 live births and stillbirths
  • infant mortality rate: number of deaths at ages under 1 year, per 1,000 live births
  • perinatal mortality rate: number of stillbirths plus number of deaths at ages under 7 days, per 1,000 live births and stillbirths
  • early neonatal mortality rate: number of deaths at ages under 7 days, per 1,000 live births
  • neonatal mortality rate: number of deaths at ages under 28 days, per 1,000 live births
  • postneonatal mortality rate: number of deaths at ages 28 days and over, but under 1 year, per 1,000 live births
  • age-specific child mortality rate: number of deaths in a particular age group per 100,000 population in that group
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4. Referral to the coroner

While the majority of infant deaths are certified by a doctor, some may be reported to the coroner by the certifying doctor or the registrar. The circumstances under which a death has to be referred are covered in the User guide to mortality statistics.

Table 1 provides the numbers of deaths by method of certification for those infants aged under 1 year, in 2015. Stillbirths may be certified by the medical practitioner or the midwife who is present at or who conducts the delivery, or who examines the body after birth. In 2015, 68% were certified by midwives and 30% by doctors.

The conditions for certifying neonatal deaths are as for other deaths – that the doctor should have been in attendance during the deceased’s last illness, should have seen the patient prior to death or seen the body and that the cause of death is known and is “natural”.

Inquests on stillbirths and neonatal deaths are rare. In 2015 86% of neonatal deaths were certified by a doctor and 12% by a coroner, with only 5% subject to a coroner’s inquest. This reflects the fact that nearly all neonatal deaths occur in hospitals and that infant deaths can be certified as due to sudden infant death syndrome (SIDS) without being subject to inquest.

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5. Area coverage and base populations

5.1 Area coverage

The births and deaths recorded in the annual publication Child mortality statistics and Birth cohort tables are those occurring in a given calendar year that have been registered in England and Wales.

Births and deaths to residents of England and Wales that occur and are registered outside of England and Wales are excluded. Births and deaths registered in England and Wales to persons whose usual residence is outside England and Wales are included in any total figures for England and Wales, but are excluded from any sub-division of England and Wales. Figures for live births and stillbirths to women whose usual residence is outside of England and Wales can be found in Tables 5 and 6 in the publication Birth characteristics.

Table 2 gives recent numbers of infant deaths that occurred in England and Wales in a given year for those infants not usually resident in England and Wales.

5.2 Base populations

The population figures used to calculate child mortality rates are mid-year estimates of the resident population of England and Wales based on the Census of Population. Our mid-year population estimates are based on updates from the most recent census allowing for births, deaths, net migration and ageing of the population.

The population estimates used for the calculation of mortality rates are the latest consistent estimates available at the time of production. Further information on population estimates and their methodology can be found on our website.

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6. Coding the underlying cause of death

For deaths at ages 28 days and over, the death certificate (Annex D) used in England and Wales accords with that recommended by the World Health Organisation (WHO) in the tenth revision of the International Statistical Classification of Diseases and Related Health Problems (ICD-10) (WHO 1992 to 1994). Further information regarding coding the underlying cause of death can be found in the User guide to mortality statistics.

On 1 January 2014, ONS changed the software used to code cause of death from MMDS to IRIS. The new IRIS software version 2013 incorporates official updates to ICD-10 that are approved by WHO. The use of the IRIS software will help to improve the international comparability of mortality statistics. For stillbirths and neonatal deaths, any maternal condition mentioned on the death certificate will be coded to the P chapter (certain conditions originating in the perinatal period) rather than elsewhere in the ICD classification. Previously these deaths may have been coded to the O chapter (pregnancy, childbirth and the puerperium). The 2014 registrations of stillbirths and neonates that occurred in 2013 were recoded to ensure comparability within the 2013 occurrences dataset. Although this change was implemented on 1 January 2014 there were a very small number of infant deaths that occurred in 2013 and were registered in 2014, that were affected by the change.

Further information on IRIS can be found on our website. There is also a study that looks into the impact of the coding changes on stillbirths and neonatal deaths.

6.1 Neonatal and stillbirth cause of death certificates

The neonatal and stillbirth certificates (Annex D), introduced in January 1986 follow recommendations of WHO in the ICD, whereby causes of death are given separately in the following categories:

  • main diseases or conditions in infant or fetus
  • other diseases or conditions in infant or fetus
  • main maternal diseases or conditions affecting infant or fetus
  • other maternal diseases or conditions affecting infant or fetus
  • other relevant causes

While conditions arising in the mother that affected the infant could be mentioned on certificates prior to 1986, no provision was made for those cases in which the certifier considered that both maternal and infant conditions contributed to the death. The current certificates overcome this problem. However, since equal weighting is given to main conditions in the infant and in the mother, it is no longer possible to identify a single underlying cause of death for neonatal deaths and stillbirths.

6.2 ONS cause of death groups

In England and Wales, stillbirths and neonatal deaths are registered using a special death certificate (Annex D), which enables reporting of relevant diseases or conditions in both the infant and the mother. For postneonatal deaths, a single underlying cause of death can be reported using the standard death certificate. ONS has developed a hierarchical classification system producing broad cause groups to enable direct comparison of neonatal and postneonatal deaths. The hierarchical classification, which is referred to as the ONS cause groups, allows the death to be assigned to a specific category, based on the likely timing of the damage leading to the death. A computer algorithm directs any mention, in the case of neonatal deaths and underlying cause in the case of postneonatal deaths, to the first appropriate class of the following mutually exclusive categories:

Before the onset of labour:

1 Congenital anomalies
2 Antepartum infections
3 Immaturity related conditions

In, or shortly after labour:

4 Asphyxia, anoxia, or trauma

Postnatal:

5 External conditions
6 Infections
7 Other specific conditions
9 Sudden infant deaths

Unclassified:

0 Other conditions

A similar algorithm is used for stillbirths.

The grouping of ICD-10 codes into these nine categories for neonatal and postneonatal deaths is shown in Annex B and Annex C respectively. Corresponding groupings for stillbirths are shown in Annex A. (Annexes A.1, B.1 and C.1 refer to 2001 to 2010, Annexes A.2, B.2 and C.2 refer to 2011 to 2013 and Annexes A.3, B.3 and C.3 refer to 2014 onwards).

However, for the data years 2001 to 2012, postneonatal deaths were assigned to the ONS cause groups based on mentions rather than underlying cause. Some analysis of the impact of this change in methods is available on request.

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7. Linkage of births and deaths

The linkage of birth and infant death records has been conducted since 1975 to obtain information on the social and biological factors of the baby and parents collected at birth registration.

Death registration gives only a limited amount of information about the parents of the deceased infant, for example, occupation of parent. However, a considerable amount of information is given at birth registration. This includes: age of each parent, number of previous children born to the mother, country of birth of parents, place of birth and whether the baby was a singleton or multiple birth.

The unlinked cases can be split into two groups: those that cannot be linked (such as those born outside England and Wales, foundlings and adopted children) and others that should have been linked but for which no birth registration record could be found. Around 1% of infant deaths cannot be linked to a birth registration record.

7.1 Socio-economic classification as defined by occupation

The information on occupation of one parent is coded for all infants dying in the first year of life, and for all stillborn babies. However, it is only coded for a sample of 1-in-10 live births. Combining this with the employment status, a code for socio-economic classification (or social class in previous volumes) may be derived. In tables displaying socio-economic classification, the live birth figures for each socio-economic classification have therefore been grossed up by a multiple of 10. The socio-economic classification breakdowns do not total the “All” rows totals, which are based on the full births and death extracts totals.

From 1991 to 2000, occupation was coded using the Standard Occupational Classification SOC90 and occupation codes were allocated to the Registrar General’s Social Class. Since 2001, the National Statistics Socio-economic Classification (NS-SEC) has categorised the socio-economic classification of people.

The Standard Occupational Classification is revised every 10 years and in 2011 SOC2010 replaced SOC2000. A report outlining the impact of re-basing the NS-SEC on SOC2010 is available on our website.

NS-SEC has eight analytic classes, the first of which can be subdivided:

1 Higher managerial and professional occupations
  1.1 Large employers and higher managerial occupations
  1.2 Higher professional occupations
2 Lower managerial and professional occupations
3 Intermediate occupations
4 Small employers and own-account workers
5 Lower supervisory and technical occupations
6 Semi-routine occupations
7 Routine occupations
8 Never worked and long-term unemployed

Students, occupations not stated or inadequately described and occupations not classifiable for other reasons are added as “Not classified”.

Up until the 2011 data year, ONS published child mortality and birth statistics by NS-SEC using the father’s NS-SEC. Historically, the decision to use father’s NS-SEC was based on the premise that many mothers either do not have a paid occupation or choose not to state their occupational details at birth registration.

From the 2012 data year, we have used the combined method for reporting NS-SEC for birth and child mortality statistics (using the most advantaged NS-SEC of either parent and creating a household level classification rather than just using the father’s classification).

7.2 Births within or outside marriage or civil partnership, and sole and joint registration

Since 1 September 2009, 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. The Act also made provision for two men to be officially recognised as the parents of a child through the provision of a parental order, obtainable through the courts. Due to small numbers, births registered within a civil partnership are included with births registered within marriage. Births registered to a same-sex couple outside of a civil partnership are combined with births outside marriage. Given the relatively small numbers of births registered to same-sex couples, the impact on statistics is negligible.

A birth within marriage or civil partnership is that of a child born to parents who were lawfully married or in a civil partnership either:

  • at the date of the child’s birth, or
  • when the child was conceived, even if they later divorced or were granted a civil partnership dissolution or the father or second parent died before the child’s birth

Births occurring outside marriage or civil partnership may be registered either jointly or solely. A joint registration records details of both parents and requires them both to be present. A sole registration records only the mother’s details. In a few cases a joint registration is made in the absence of the father or second parent if an affiliation order or statutory declaration is provided. Information from the birth registration is used to determine whether the mother and father or second parent jointly registering a birth outside marriage or civil partnership were usually resident at the same address at the time of registration. Births with both parents at the same address are identified by a single entry for the informant’s usual address, while different addresses are identified by two entries.

Some infants born outside marriage are deemed to have been born within marriage when the natural parents subsequently marry between the infant’s birth and death. Birth registrations do not, however, identify children whose parents marry after the birth of the child. All relevant tables in Child mortality statistics and Birth cohort tables relate to marital status at birth. This ensures that the numerators and denominators used to calculate rates are compatible.

7.3 Mother’s country of birth

The birthplace of the parents of children born in England and Wales has been recorded at birth registration since 1969, but these data have been available for an infant mortality analysis of social factors only since 1975, when routine linkage was started. A breakdown of the mother’s country of birth groupings can be found alongside the published tables.

7.4 Birthweight

Birthweight is measured in grams. For live birth registrations, the birthweight is passed electronically to ONS from the notification by the midwife or doctor in attendance at the birth. These details are then supplied to the registrar. For stillbirths, details of the weight of the fetus are supplied on a certificate or notification by a doctor or midwife. The certificate or notification is then taken by an informant to the registrar.

If the birthweight is missing, but the registration is linked to the birth notification, then the birthweight from the notification is taken. In cases where no birthweight is recorded, the birth is included in the total “All weights” but not distributed among the individual categories. Any remaining missing birthweights are included in the “Not stated” total for the relevant tables containing birthweight. Annual figures for records where the birthweight was not recorded for live births and stillbirths can be found in the User guide to birth statistics.

7.5 Number of previous children

In May 2012, ONS implemented a legislative change to improve the statistical information collected at birth registration in England and Wales. Two amendments have been made to the Population (Statistics) Act 1938, the legislation that requires registrars to collect confidential information for statistical purposes. The changes were made within the Welfare Reform Act 2009.

The two amendments mean that:

  • information is now collected at all birth registrations on the total numbers of previous live births and previous stillbirths that the mother has had (not just those with the current or former husband); this has simplified the question asked by registrars and will provide improved coverage
  • information is now collected at all birth registrations on either:
    • whether the mother has been previously married or in a civil partnership (if she is currently married or in a civil partnership) or
    • whether the mother has ever been married or in a civil partnership (if she is not currently married or in a civil partnership)

This brings the birth registration process more in line with equality legislation.

Prior to May 2012, information on:

  • number of previous children with a current or former husband
  • whether the mother had previously been married

was only collected for births occurring within marriage. When the Population (Statistics) Act came into force in 1938, only 4% of live births in England and Wales occurred outside marriage so the information required was collected for nearly all mothers. However by 2011, nearly half of births (47%) took place outside marriage or civil partnership and so the legislation no longer reflected the reality of modern society.

Only minor changes have been made to published tables for 2012 and 2013 since the first full year of new data is 2013 but some childhood deaths in this year will relate to births in 2012 prior to the changes being implemented. The main improvements resulting from the amendments to the Population (Statistics) Act 1938 have been introduced to published tables for child deaths occurring in 2014. Figures for 2014 onwards are not comparable with previous years.

Although tables affected by the amendments to the Population (Statistics) Act 1938 were published for child deaths occurring in 2012 and 2013, there was a small definitional change in the data following implementation. Up to late May 2012, previous children include only those with a current or former husband, while after late May 2012 all previous children should be counted. This was not expected to have made a large difference to the figures as it is not clear how accurately the original question was understood or answered.

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8. Further information

Our website provides a comprehensive source of freely available vital statistics and ONS products. More information on our website can be obtained from the contact addresses found in the next paragraph.

Special extracts and tabulations of child mortality data for England and Wales are available to order (subject to legal frameworks, disclosure control, resources and our charging policy, where appropriate). Such enquiries should be made to Vital Statistics Outputs Branch (vsob@ons.gsi.gov.uk or telephone: +44 (0)1329 444 110). All user requested data will be published onto the website.

8.1 Other sources of information on births and deaths

Additional information on background to mortality data that we publish, together with the quality of mortality data can be found in sections 3 and 4 of the User guide to mortality statistics. Further information and background on birth statistics can be found in the User guide to birth statistics.

8.2 Other sources of data on births and deaths

Deaths occurring in a given year

Deaths registered in a given year

Summary data for infant mortality in England and Wales are available in the Deaths registrations summary tables. A geographical breakdown of infant death numbers and rates by local authority and county level is available in Deaths registered in England and Wales by area of usual residence.

The Vital statistics: population and health reference tables provide annual infant mortality data for the UK and its constituent countries.

Other UK countries

For mortality data for other UK countries please see the latest infant death statistics for Northern Ireland and the latest infant death statistics for Scotland.

Births

The Births summary tables, England and Wales provide main summary statistics for live births in England and Wales.

8.3 Other useful information

Response to the ONS review of infant mortality statistics
Results from the ICD-10 bridge coding study for stillbirths and neonatal deaths
Disclosure Control Policy for Birth and Death Statistics (currently under revision)

We welcome feedback from users on the content, format and relevance of mortality outputs.

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9. Glossary

Antepartum

Occurring just before birth.

Cause groups

The ONS cause groups is another term used for “Hierarchical classification”; see this definition.

Childhood

Children aged between 1 and 15 years.

Congenital anomaly

A structural or functional abnormality of the human body that develops before birth.

Coroner

Public official responsible for the investigation of violent, sudden or suspicious deaths.

Early neonatal

Relating to infants aged under 7 days.

Hierarchical classification

ONS' method for classifying the causes of neonatal deaths and stillbirths, made up of groups of ICD codes referred to as “ONS cause groups”.

ICD

International Classification of Diseases and Related Health Problems.

Infant deaths

Under 1 year.

Inquest

Inquiry into the cause of an unexplained, sudden or violent death, held by a coroner.

Linkage

The matching of infant death records to their corresponding birth registration record.

Neonatal

Relating to infants aged under 28 days.

NS-SEC

National Statistics Socio-economic Classification categorises the socio-economic classification of people and has replaced the Registrar General’s Social Class and the Socio-economic Group (SEG).

Occurrences

Number of deaths according to the date on which the death occurred.

ONS

Office for National Statistics.

Perinatal

Stillbirths and early neonatal.

Postneonatal

Relating to infants aged between 28 days and 1 year.

Registrar

Local authority employee responsible for the registration of births, deaths, marriages and civil partnerships.

Registrations

Number of deaths according to the date on which the deaths were registered.

SOC 2010

Standard Occupational Classification 2010 is the current occupational classification. SOC2010 codes, details of employment status and size of organisation are required for the derivation of NS-SEC. See NS-SEC.

Stillbirth

A 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.

Underlying cause of death

The cause of death selected for primary tabulation (excludes deaths at age under 28 days).

VSOB

Vital Statistics Outputs Branch (at ONS).

WHO

World Health Organisation.

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Contact details for this Methodology

Vasita Patel
vsob@ons.gsi.gov.uk
Telephone: +44 (0)1329 444110