Statistical bulletin: Infant and Perinatal Mortality in England and Wales by Social and Biological Factors, 2011

Key Findings

• In 2011 the infant mortality rate was 4.1 deaths per 1,000 live births, the lowest ever recorded for England and Wales.
• Infant mortality rates were highest among babies of mothers aged under 20 years and 40 years and over at 5.4 deaths per 1,000 live births.
• Perinatal mortality rates were also higher for mothers in the ‘under 20’ and ‘40 and over’ age groups, at 9.2 and 11.2 deaths per 1,000 live births respectively.
• Very low birthweight babies (under 1,500 grams) had the highest infant and perinatal mortality rates, at 172.1 and 260.8 deaths per 1,000 live births respectively.
• Infant mortality rates were highest for babies registered solely by their mother and those registered jointly by parents living at different addresses, at 5.7 and 5.4 deaths per 1,000 live births respectively.

Summary

This Statistical Bulletin presents statistics on infant and perinatal deaths that occurred in England and Wales in 2011. Perinatal deaths are stillbirths and deaths that occur during the first week of life. Infant deaths are those that occur in the first year of life. Neonatal deaths are deaths that occur within the first 28 days after birth; postneonatal deaths are those that occur between 28 days and 1 year after birth.

The level of infant mortality is seen as a key indicator of the health of a nation, as calculated by infant mortality rates (IMRs) – deaths at age under one year, per 1,000 live births. A range of biological and social factors are associated with high rates of infant mortality. These include birthweight, mother’s age at birth of child, mother’s country of birth, marital status, parity (the total number of births a woman has had previously) and father’s socio-economic status based on his occupation.

In 2011, there were 3,032 infant deaths in England and Wales of which 2,962 (97.7 per cent) were linked to their corresponding birth records. The linkage rate for 2011 is comparable with that for previous years. This linkage enables analysis of infant and perinatal deaths by risk factors collected at birth registration.

In 2011 the infant mortality rate was 4.1 deaths per 1,000 live births. The majority of all linked infant deaths, 2,095 (70.7 per cent), occurred during the neonatal period (under 28 days of life). The neonatal mortality rate (2.9 deaths per 1,000 live births) was more than twice the post-neonatal mortality rate (1.2 deaths per 1,000 live births). Between 2000 and 2011 the infant mortality rate decreased by 25 per cent from 5.5 to 4.1 deaths per 1,000 live births (Table 1 and Figure 1). This change is statistically significant.

There has been little change in the stillbirth rate, which has fluctuated between 5.1 and 5.7 stillbirths per 1,000 births since 2000. In 2011 the stillbirth rate was 5.2 stillbirths per 1,000 births. No changes over the period were statistically significant.

Figure 1 Stillbirths and linked infant deaths, 2000–2011

Source: Office for National Statistics

Notes:

1. Data for 2011 are provisional.
2. Stillbirth deaths per 1,000 live births and stillbirths. Neonatal, postneonatal and infant deaths per 1,000 live births.

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Biological factors

Biological factors such as birthweight, mother’s age and parity (the total number of births a woman has had previously) are key determinants of infant mortality.

In 2011, around 1 in 14 live births (7.0 per cent) were classed as ‘low birthweight’ (under 2,500 grams). More than 92 per cent of live births were considered ‘normal’ birthweight (2,500 grams and over), of which, more than two-fifths (40.5 per cent) were classed as 3,500 grams and over.

In 2011, the infant mortality rates for very low birthweight babies (under 1,500 grams) and low birthweight babies (under 2,500 grams) were 172.1 and 36.4 deaths per 1,000 live births respectively, compared with a rate of 1.4 deaths per 1,000 live births among babies of normal birthweight (2,500 grams and over) (Table 2).

Low birthweight can be a result of poor growth, prematurity or both and data about gestational age are needed to distinguish between the two (Kurinczuk et all, 2009). Information about gestational age is not collected for live births at registration; the Statistical Bulletin ‘Gestation-specific infant mortality in England and Wales’ links birth registrations to birth notifications and presents data about births and neonatal and infant mortality by gestational age. Information about gestation is collected for stillbirths at registration.

In 2011, the majority of very low birthweight babies (under 1,500 grams) who were stillborn were also of low gestational age (24–27 weeks). Two-thirds of stillbirths (65.9 per cent) were preterm (less than 37 completed weeks of gestation), of which, almost two-thirds (63.8 per cent) belonged to the very low birthweight category (Table 3).

Infant mortality rates vary by mother’s age at the time of birth of the baby. The age at which women have children has been shown to be related to their socio-economic status, job opportunities, access to further education and training in their employment (Cooper 2001). However, for very young mothers, increased risk of adverse birth outcomes is independent of known risk factors such as low socio-economic status, marital status, education and inadequate pre-natal care (Chen et al, 2007, Cooper, Leland and Alexander 1995).

In 2011 the infant mortality rate was highest among babies of mothers aged under 20 years and mothers aged 40 years and over (both at 5.4 deaths per 1,000 live births). Babies who were born to mothers aged between 35 and 39 years had the lowest infant mortality rate (3.7 deaths per 1,000 live births).

Babies of mothers aged 40 years and over had the highest stillbirth and perinatal mortality rates at 8.0 and 11.2 per 1,000 births respectively. Babies of mothers aged 20 years and under had the highest postneonatal mortality rates at 2.1 per 1,000 total births (Table 4). Figure 2 shows infant mortality and stillbirth rates in 2011 by mother’s age.

Figure 2 Stillbirths and infant deaths by mother's age, 2011

Source: Office for National Statistics

Notes:

1. Data for 2011 are provisional.
2. Stillbirths and perinatal deaths per 1,000 live births and stillbirths. Neonatal, postneonatal and infant deaths per 1,000 live births.

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Infant mortality rates also vary by birth registration type, which is determined from the child’s birth records (Table 5). There are four ‘birth registration type’ categories: within lawful marriage, jointly registered by both parents outside of marriage at the same address, joint registration outside marriage with parents at different addresses and births solely registered by the mother.

The registration types with the highest infant mortality rates were births registered solely by the mother (5.7 deaths per 1,000 live births) and births outside marriage registered jointly by both parents living at different addresses (5.4 per 1,000 live births). Sole registered births also had the highest stillbirth rate at 6.8 per 1,000 births. Many sole registered births are to younger women: in 2011, 20.5 per cent of all births to women under 20 were sole registrations, compared with 3.1 per cent to women aged between 30 and 34 years.

Until May 2012, parity – the total number of births a woman has had previously – was only recorded for married women. The infant mortality rate was highest among mothers with three or more previous children (5.0 deaths per 1,000 live births) and lowest among mothers with one previous child (2.8 deaths per 1,000 live births). Figure 3 shows stillbirth and mortality rates in 2011 by parity.

From May 2012 onwards information has been 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). Figures on parity for all previous births will be reported on in 2014 when data will be available for the full year.

Figure 3 Stillbirths and infant deaths by parity (within marriage), 2011

Source: Office for National Statistics

Notes:

1. Data for 2011 are provisional.
2. Stillbirths and perinatal deaths per 1,000 live births and stillbirths. Neonatal, postneonatal and infant deaths per 1,000 live births.

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Social factors

Infant mortality rates vary with social factors such as mother’s country of birth and the socio-economic position of the family, as derived from the information about the occupation of the father given at the registration of the birth.

Figure 4 shows rates in 2011 for stillbirths, perinatal and infant mortality by mother’s region of birth. Babies with mothers born in Africa (5.9 deaths per 1,000 live births), the Americas and the Caribbean (4.8 deaths per 1,000 live births) and the Middle East and Asia (4.7 deaths per 1,000 live births) had high infant mortality rates compared with the overall infant mortality rate of 4.1 deaths per 1,000 live births (see Mother's country of birth groupings).

The perinatal mortality rate was also high in babies of mothers born in Africa (11.8 deaths per 1,000 births), the Middle East and Asia (9.0 deaths per 1,000 births) and the Americas and the Caribbean (8.0 deaths per 1,000 births) compared with babies of mothers born in the UK (7.1 deaths per 1,000 births). Table 6 in the downloadable reference tables presents a more detailed breakdown of mother’s country of birth.

Figure 4 Stillbirths and infant deaths by mother's region of birth, 2011

Notes:

1. Data for 2011 are provisional.
2. Stillbirths and perinatal deaths per 1,000 live births and stillbirths. Infant deaths per 1,000 live births.
3. Including Isle of Man and Channel Islands.
4. The 'New EU' constitutes twelve countries which have joined the European Union since 2004. The twelve countries which have joined the European Union since 2004 are included in both the 'New EU' and the 'EU' categories.
5. Includes Europe not otherwise stated.
6. Includes Africa not otherwise stated.
7. Includes Asia (except Middle East) not otherwise stated.
8. Includes Antarctica and Antarctica and Oceania not otherwise stated.

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The age at which women have children has been shown to be related to their socio-economic status (Cooper, 2011) and significant differences in infant mortality rates by socio-economic group persist in England and Wales (Oakley et. al. 2009).

Using the father’s occupation and employment status as a proxy for socio-economic status (and therefore excluding births registered solely by the mother), infant mortality rates were highest for babies of married fathers in routine occupations (5.2 deaths per 1,000 live births) and babies of unmarried father’s in semi-routine occupations (5.0 deaths per 1,000 live births).

Fathers classified to the ‘Other’ category comprise a mixed group including those who have never worked, the long term unemployed, students and those individuals whose occupational details could not be classified. Although babies in this group had the highest rates for stillbirths and perinatal deaths, these figures should be interpreted with caution because the rates may vary between the different sub-groups within this category (Table 7).

Causes of death

In England and Wales, stillbirths and neonatal deaths are registered using a special death certificate 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 (Dattani & Rowan, 2002).

In January 2011, the Office for National Statistics (ONS) introduced a new version of the 10th revision of the International Classification of Diseases (ICD–10) used to code cause of death. A recent study (Messer, 2011) found no impact on the ONS broad cause groups. For more information see the full bulletin.

Almost three-quarters (74.0 per cent) of all infant deaths and 85.9 per cent of all neonatal deaths were related to events occurring before the onset of labour (that is, congenital anomalies, antepartum infections and immaturity related conditions).

For postneonatal deaths, 30.3 per cent were related to congenital anomalies, 14.6 per cent were sudden infant deaths, 14.4 per cent were from immaturity related conditions and 14.1 per cent were from infections. The majority of stillbirths (75.2 per cent) were classified as antepartum deaths (Table 8).

Users and uses of Infant mortality by social and biological factors statistics

This report on infant and perinatal mortality is an annual output, produced as a statistical bulletin. Figures are published for infant and perinatal mortality by baby’s age at death; birthweight; mother’s age; mother’s country of birth; marital status and type of registration and father’s occupation at registration of birth and death.

The report also presents figures for stillbirths by gestation and birthweight. Birthweight as a risk factor is presented as a grouped variable to draw distinction between death rates for low and normal birthweight babies. Deaths by mother’s age at the time of baby’s birth provides for useful comparison between younger and older age groups.

One of the key users of these statistics is the Department of Health (DH). Infant mortality continues to take a central role in DH’s work on health inequalities. Other users of this output include academics, independent researchers and the media.

Policy context

Infant mortality rates have been falling over the last few years and are at an all-time record low. However, health inequalities, such as differences in infant mortality rates by socio-economic group, persist.

The NHS Outcomes Framework 2012/13 includes the domain ‘Preventing people from dying prematurely’. Indicator 1.6 of this domain is Infant mortality: rate per 1,000 live births.

Further Information

Tables in this report

Table 1   Infant deaths and infant mortality rates: all and linked deaths, 2000–2011

Table 2   Live births, stillbirths and infant deaths by birthweight, 2011

Table 3   Stillbirths: Gestation by birthweight, 2011

Table 4   Live births, stillbirths and infant deaths by mother’s age, 2011

Table 5   Live births, stillbirths and infant deaths by marital status, parity (within marriage) and type of registration, 2011

Table 6   Live births, stillbirths and infant deaths by mother’s country of birth, 2011

Table 7   Live births, stillbirths and infant deaths by National Socio–economic classification (NS-SEC), 2011

Table 8   Live births, stillbirths and infant deaths by ONS cause groups, 2011

Child mortality statistics presents statistics on infant deaths and childhood deaths occurring annually in England and Wales. Gestation-specific infant mortality presents data on live births and infant deaths by gestational age. Unexplained deaths in infancy includes both sudden infant deaths and deaths for which the cause remains unascertained.

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

Mother’s Country of Birth Groupings

United Kingdom

England, Northern Ireland, Scotland, Wales, Alderney, Sark (Little and Great), Guernsey, Jersey, Channel Islands not otherwise specified, Isle of Man, Great Britain not otherwise stated, United Kingdom not otherwise specified.

New EU

Estonia, Latvia, Lithuania, Czech Republic, Hungary, Poland, Romania, Slovakia, Malta, Bulgaria, Cyprus (EU), Cyprus (not otherwise stated), Slovenia, Czechoslovakia not otherwise stated.

EU

Austria, Belgium, Bulgaria, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Poland, Portugal, Romania, Slovakia, Slovenia, Sweden, Cyprus (EU), Cyprus (not otherwise stated), Spain (except Canary Islands), Spain not otherwise stated, Aland Islands, Vatican City, Czechoslovakia not otherwise specified, Canary Islands.

Rest of Europe

Europe not otherwise stated, Albania, Bosnia and Herzegovina, Croatia, Cyprus (non EU), Kosovo, Macedonia, Montenegro, Serbia, Turkey, Serbia and Montenegro not otherwise specified, Andorra, Gibraltar, San Marino, Armenia, Azerbaijan, Belarus, Georgia, Moldova, Russia, Ukraine, Faroe Islands, Iceland, Norway, Svalbard and Jan Mayen, Liechtenstein, Monaco, Switzerland, Union of Soviet Socialist Republics not otherwise stated, Yugoslavia not otherwise stated, Commonwealth of (Russian) Independent States.

Africa

North Africa, Western Africa, Central Africa, Eastern Africa, Southern Africa, Africa not otherwise stated.

North Africa

Algeria, Egypt, Libya, Morocco, Sudan, Tunisia, Western Sahara.

Western Africa

Benin, Burkina, Cape Verde, Ivory Coast, The Gambia, Guinea, Guinea-Bissau, Liberia, Mali, Mauritania, Niger, Nigeria, St Helena, Senegal, Sierra Leone, Togo.

Central Africa

Angola, Cameroon, Central African Republic, Chad, Congo, Democratic Republic of Congo, Equatorial Guinea, Gabon, Sao Tome and Principe.

Eastern Africa

Burundi, Comoros, Djibouti, Eritrea, Ethiopia, Kenya, Madagascar, Malawi, Mauritius, Mayotte, Mozambique, Reunion, Rwanda, Seychelles, Somalia, Tanzania, Uganda, Zambia, Zimbabwe.

Southern Africa

Botswana, Lesotho, Namibia, South Africa, Swaziland.

The Americas and the Caribbean

North America, Central America, South America, The Caribbean.

North America

Bermuda, Canada, Greenland, Saint Pierre and Miquelon, United States of America, North America not otherwise stated.

Central America

Belize, Costa Rica, El Salvador, Guatemala, Honduras, Mexico, Nicaragua, Panama, Central America not otherwise stated.

South America

Argentina, Bolivia, Brazil, Chile, Colombia, Ecuador, Falkland Islands, South Georgia and the South Sandwich Islands, French Guiana, Guyana, Paraguay, Peru, Surinam, Uruguay, Venezuela, South America not otherwise stated.

The Caribbean

Antigua and Barbuda, Anguilla, Aruba, The Bahamas, Barbados, British Virgin Islands, Cayman Islands, Cuba, Dominica, Dominican Republic, Grenada, Guadeloupe, Haiti, Jamaica, Martinique, Montserrat, Netherlands Antilles, Puerto Rico, St Barthelemy, St Kitts and Nevis, St Lucia, St Martin (French Part), St Vincent and the Grenadines, Trinidad and Tobago, Turks and Caicos Islands, United States Virgin Islands, Caribbean not otherwise stated.

Middle East and Asia

Middle East, Central Asia, Eastern Asia, Southern Asia, South East Asia, Asia not otherwise specified.

Middle East

Bahrain, Iran, Iraq, Israel, Jordan, Kuwait, Lebanon, Oman, Qatar, Saudi Arabia, Syria, United Arab Emirates, Occupied Palestinian Territories, Yemen, Middle East not otherwise specified.

Central Asia

Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan, Uzbekistan.

Eastern Asia

China, Hong Kong, Japan, North Korea, South Korea, Macao, Mongolia, Taiwan.

Southern Asia

Afghanistan, Bangladesh, Bhutan, India, Maldives, Nepal, Pakistan, Sri Lanka.

South East Asia

Brunei, Burma, Cambodia, East Timor, Indonesia, Laos, Malaysia, Philippines, Singapore, Thailand, Vietnam.

Antarctica and Oceania

Antarctica, Australasia, Other Oceania.

Antarctica

Antarctica, Bouvet Island, French Southern Territories.

Australasia

Australia, Christmas Island, Cocos (Keeling) Islands, New Zealand, Norfolk Island.

Other Oceania

American Samoa, British Indian Territory, Cook Islands, Fiji, French Polynesia, Guam, Heard Islands and McDonald Islands, Kiribati, Marshall Islands, Micronesia, Nauru, New Caledonia, Niue, Northern Mariana Islands, Palau, Papua New Guinea, Pitcairn, Henderson, Ducie and Oeno Islands, Samoa, Solomon Islands, Tokelau, Tonga, Tuvalu, United States Minor Outlying Islands, Vanuatu, Wallis and Futuna, Caroline Islands, New Hebrides.

National Statistics Socio-economic Classification (NS-SEC): eight analytic class version, with examples

1. Higher managerial and professional occupations

Directors and chief executives of major organisation, civil engineers, medical practitioners, IT strategy and planning professionals, legal professionals, architects, senior officials in national and local government.

2. Lower managerial and professional occupations

Teachers in primary and secondary schools, quantity surveyors, public service administrative professionals, social workers, nurses, IT technicians.

3. Intermediate occupations

Graphics designers, medical and dental technicians, Civil Service administrative officers and local government clerical officers, counter clerks, school and company secretaries.

4. Small employers and own account workers

Hairdressing and beauty salon proprietors, shopkeepers, dispensing opticians in private practice, farmers, self-employed decorators.

5. Lower supervisory and technical occupations

Bakers and flour confectioners, catering supervisors, head waitresses/waiters, postal supervisors, sales assistants supervising others.

6. Semi-routine occupations

Retail assistants, catering assistants, clothing cutters, dressmaker, traffic wardens, veterinary nurses and assistants, shelf fillers.

7. Routine occupations

Hairdressing employees, floral arrangers, sewing machinists, bar staff, cleaners and domestics.

Other

Full-time students, never worked, long-term unemployed, inadequately described, not classifiable for other reasons.

Source: NS-SEC User Manual, Office for National Statistics  (Office for National  Statistics 2001, see references).

References

Chen XK, Wen SW, Fleming N, Demissie K, Rhoads GG, Walker M (2007) ‘Teenage pregnancy and adverse birth outcomes: a large population  based retrospective cohort study’, International Journal of Epidemiology, Volume 36, Issue 2, pp 368-373

Cooper, N (2001) ‘Analysis of infant mortality rates by risk factors and by cause of death in England and Wales’ In: Griffiths, Clare. Fitzpatrick, Justine. (Eds) DS 16. Decennial Supplement: Geographic Variations in Health. Stationery Office.

Cooper LG, Leland NL, and Alexander G (1995) ‘Effect of maternal age on birth outcomes among young adolescents’, Biodemography and Social Biology, Volume 42, Issue 1-2, 1995

Dattani N and Rowan S (2002) ‘Causes of neonatal deaths and stillbirths: a new hierarchical classification in ICD–10’, Health Statistics Quarterly 15, 16–22 (72.2 Kb Pdf) .

Department of Health (2010) ‘Healthy Lives, Healthy People: our strategy for public health in England’.

Department of Health (2011) ‘The NHS Outcomes Framework 2012/2013’.

Department of Health (2012) ‘Healthy lives, healthy people: Improving outcomes and supporting transparency’.

Marmot Review (2010) ‘Fair Society, Healthy Lives’.

Messer (2011) ‘Results of the ICD-10 v2010 bridge coding study for stillbirths and neonatal deaths, England and Wales, 2009’.

Office for National Statistics (2001) The National Statistics Socio–economic Classification.

Background notes

1. Definitions used in infant mortality statistics:

   Stillbirth – born after 24 or more weeks completed gestation and which did not, at any time, breathe or show signs of life Early neonatal – deaths under seven days

   Perinatal – stillbirths and early neonatal deaths

   Neonatal – deaths at under 28 days

   Postneonatal – deaths between 28 days and one year

   Infant – deaths under one year

   Rates – stillbirths and perinatal mortality rates reported per 1,000 total births (live and stillbirths). Neonatal, postneonatal and infant mortality rates are reported per 1,000 live births. 

2. This report is based on data available up to 26 September 2012 and figures for 2011 are provisional. Figures reported in Table 1 for 2000 to 2010 are final. Final data for 2011 will be published in ‘Child mortality statistics: Childhood, infant and perinatal – 2011’ in early 2013.

3. A Summary Quality Report for this release is available on the Office for National Statistics website. Further information on data quality, legislation and procedures relating to childhood, infant and perinatal mortality is available on the ONS website in Child Mortality Statistics Metadata. More general information on the collection, production and quality of mortality data is available in Mortality Metadata.

4. Details of the associated ICD–10 codes allocated to stillbirths, neonatal deaths and postneonatal deaths can be found in Annex A, B and C respectively in Child Mortality Statistics Metadata. Available on the Office for National Statistics website.

5. Special extracts and tabulations of infant mortality data for England and Wales are available to order (subject to legal frameworks, disclosure control and agreement of costs, where appropriate, see ONS charging policy. For such requests, enquiries should be made to:

   Mortality Analysis Team, Life Events and Population Sources

   Office for National Statistics
   Government Buildings
   Cardiff Road
   Newport
   Gwent NP10 8XG
   Tel: +44 (0)1633 456398  
   E-mail: CIM@ons.gsi.gov.uk

6. As a valued user of our statistics, we would welcome feedback on this release. In particular, the content, format and structure. This is in line with the Health and Life Events user engagement strategy, available to download from the ONS website. -division--hled----user-engagement-strategy-and-plan/user-engagement-strategy-and-plan.pdf.

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8. Next publication: November 2013

9. Details of the policy governing the release of new data are available by visiting www.statisticsauthority.gov.uk/assessment/code-of-practice/index.html or from the Media Relations Office email: media.relations@ons.gsi.gov.uk

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