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  World infant mortality rates in 2008^[1]

In the field of public health, infant mortality is a commonly used statistical measure that is defined as the ratio of infant deaths to live births.

Traditionally, the most common cause worldwide was dehydration from diarrhea, however a variety of programs combating this problem have decreased the rate of children dying from dehydration. As a result, the most common cause is now pneumonia. Other major causes of infant mortality include: malnutrition, malaria, congenital malformation, infection and SIDS.

In reliability engineering, "infant mortality" is the failures that occur in the first part of the bathtub curve.

  Common definitions

The most widely used definition of Infant mortality rate (IMR) is the number of deaths of babies under one year of age per 1,000 live births. The rate in a given region, therefore, is the total number of newborns dying under one year of age divided by the total number of live births during the year, then all multiplied by 1,000. The infant mortality rate is also called the infant death rate (per 1,000 live births).

Historically, infant mortality claimed a considerable percentage of children born, in the 1850s in America it was estimated to be 216.8 per 1,000 for whites and 340.0 for African Americans but rates have significantly declined in the West in modern times. This has been mainly due to improvements in basic health care, though high-technology medical advances have also helped. Infant mortality rate is commonly included as a part of standard of living evaluations in economics.^[2]

  Global infant mortality trends

For the world, and for both Less Developed Countries (LDCs) and More Developed Countries (MDCs), IMR declined significantly between 1960 and 2001. According to the Save the Children State of the World's Mothers report, the world infant mortality rate declined from 126 in 1960 to 57 in 2001.^[4]

However, IMR was, and remains, higher in LDCs. In 2001, the Infant Mortality Rate for Less Developed Countries (91) was about 10 times as large as it was for More Developed Countries (8). For Less Developed Countries, the Infant Mortality Rate is 17 times as high as it is for More Developed Countries. Also, while both LDCs and MDCs made dramatic reductions in infant mortality rates, reductions among less developed countries are, on average, much less than those among the more developed countries.

Nearly two orders of magnitude separate countries with the highest and lowest reported infant mortality rates. The top and bottom five countries by this measure (taken from The World Factbook's 2009 estimates) are shown below.

Afghanistan's infant mortality rate is expected to improved by at least 60% in the next ten years due to billions of dollars of international aid.^[5]

  Socio-economic factors

Social class is a major factor in infant mortality, both historically and today. Over the period between 1912 and 1915, the Children’s Bureau examined data across eight cities and nearly 23,000 live births.^[6] They discovered that lower incomes tend to correlate with higher infant mortality. If the father had no income, the rate of infant mortality was 357% more than that for the highest income earners ($1,250+).^[6] As well, differences between races were apparent during this time period. African-American mothers experience an infant mortality at a rate 44% higher than average.^[6]

While infant mortality is normally negatively correlated with GDP, there may indeed be some opposing short-term effects to a recession. A recent study by The Economist shows that economic slowdowns reduce the amount of air pollution, which results in a lower infant mortality rate. During the late 1970s and early 1980s, the recession’s impact on air quality is estimated to have saved around 1,300 US babies.^[7] It is only during deep recessions that infant mortality increases. According to Norbert Schady and Marc-Francois Smitz, recessions where GDP per capita drops by 15% or more have a negative impact on infant mortality.^[8]

  Comparing infant mortality rates

The infant mortality rate correlates very strongly with, and is among the best predictors of, state failure.^[9] IMR is therefore also a useful indicator of a country's level of health or development, and is a component of the physical quality of life index. However, the method of calculating IMR often varies widely between countries, and is based on how they define a live birth and how many premature infants are born in the country. The World Health Organization (WHO) defines a live birth as any born human being who demonstrates independent signs of life, including breathing, voluntary muscle movement, or heartbeat. Many countries, however, including certain European states and Japan, only count as live births cases where an infant breathes at birth, which makes their reported IMR numbers somewhat lower and raises their rates of perinatal mortality.^[10]

The exclusion of any high-risk infants from the denominator or numerator in reported IMRs can be problematic for comparisons. Many countries, including the United States, Sweden and Germany, count an infant exhibiting any sign of life as alive, no matter the month of gestation or the size, but according to United States Centers for Disease Control (CDC) researchers,^[11] some other countries differ in these practices. All of the countries named adopted the WHO definitions in the late 1980s or early 1990s,^[12] which are used throughout the European Union.^[13] However, in 2009, the US CDC issued a report that stated that the American rates of infant mortality were affected by the United States' high rates of premature babies compared to European countries. It also outlined the differences in reporting requirements between the United States and Europe, noting that France, the Czech Republic, Ireland, the Netherlands, and Poland do not report all live births of babies under 500 g and/or 22 weeks of gestation.^{[11][14][dead link][15]} The report concluded, however, that the differences in reporting are unlikely to be the primary explanation for the United States’ relatively low international ranking.^[15]

Another well-documented example also illustrates this problem. Until the 1990s, Russia and the Soviet Union did not count, as a live birth or as an infant death, extremely premature infants (less than 1,000 g, less than 28 weeks gestational age, or less than 35 cm in length) that were born alive (breathed, had a heartbeat, or exhibited voluntary muscle movement) but failed to survive for at least seven days.^[16] Although such extremely premature infants typically accounted for only about 0.5% of all live-born children, their exclusion from both the numerator and the denominator in the reported IMR led to an estimated 22%-25% lower reported IMR.^[17] In some cases, too, perhaps because hospitals or regional health departments were held accountable for lowering the IMR in their catchment area, infant deaths that occurred in the 12th month were "transferred" statistically to the 13th month (i.e., the second year of life), and thus no longer classified as an infant death.^[18]

UNICEF uses a statistical methodology to account for reporting differences among countries:

Another challenge to comparability is the practice of counting frail or premature infants who die before the normal due date as miscarriages (spontaneous abortions) or those who die during or immediately after childbirth as stillborn. Therefore, the quality of a country's documentation of perinatal mortality can matter greatly to the accuracy of its infant mortality statistics. This point is reinforced by the demographer Ansley Coale, who finds dubiously high ratios of reported stillbirths to infant deaths in Hong Kong and Japan in the first 24 hours after birth, a pattern that is consistent with the high recorded sex ratios at birth in those countries. It suggests not only that many female infants who die in the first 24 hours are misreported as stillbirths rather than infant deaths, but also that those countries do not follow WHO recommendations for the reporting of live births and infant deaths.^[20]

Another seemingly paradoxical finding is that when countries with poor medical services introduce new medical centers and services, instead of declining the reported IMRs often increase for a time. This is mainly because improvement in access to medical care is often accompanied by improvement in the registration of births and deaths. Deaths that might have occurred in a remote or rural area, and not been reported to the government, might now be reported by the new medical personnel or facilities. Thus, even if the new health services reduce the actual IMR, the reported IMR may increase.

  Infant mortality rate in war

In most cases, war-affected areas will experience a significant increase in infant mortality rates. The primary causes of the increase are external factors such as murder and abuse. However, many other significant factors influence infant mortality rates in war-torn areas. Health care systems in developing countries in the midst of war often collapse. Attaining basic medical supplies and care becomes increasingly difficult. During the Yugoslav Wars in the 1990s Bosnia experienced a 60% decrease in child immunizations. Preventable diseases can quickly become epidemic given the medical conditions during war.^[21]

Many developing countries rely on foreign aid for basic nutrition. Transport of aid becomes significantly more difficult in times of war. In most situations the average weight of a population will drop substantially.^[22] Expecting mothers are affected even more by lack of access to food and water. During the Yugoslav Wars in Bosnia the number of premature babies born increased and the average birth weight decreased.^[21]

There have been several instances in recent years of systematic rape as a weapon of war. Women who become pregnant as a result of war rape face even more significant challenges in bearing a healthy child. Studies suggest that women who experience sexual violence before or during pregnancy are more likely to experience infant death in their children.^[23][24][25] Causes of infant mortality in abused women range from physical side effects of the initial trauma to psychological effects that lead to poor adjustment to society. Many women who became pregnant by rape in Bosnia were isolated from their hometowns making life after childbirth exponentially more difficult.^[26]

  See also

• List of countries by infant mortality rate
• Diarrheal diseases
• Childlessness
• Rotavirus
• Pneumonia
• Pneumococcal disease

Related statistical categories:

• Perinatal mortality only includes deaths between the foetal viability (22 weeks gestation) and the end of the 7th day after delivery.
• Neonatal mortality only includes deaths in the first 28 days of life.
• Postneonatal mortality only includes deaths after 28 days of life but before one year.
• Child mortality includes deaths within the first five years after birth.

  References

This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (January 2012)

  External links

Wikimedia Commons has media related to: Infant mortality

• The State of the World's Children 2008: Child Survival
• Infant mortality on the Children's Rights Portal
• Infant mortality rate - Country comparison
• The World Health Report 2005 – Make Every Mother and Child Count
• World Health Statistics - Probability of dying (per 1000) under age five years (under-5 mortality rate)
• World Health Statistics - Neonatal mortality rate (per 1000 live births)
• Born in Bradford - a 2006 UK-based research cohort study investigating the causes of infant mortality and low birth rate in Bradford, UK.
• State of the World's Mothers 2006 Up to date 2006 analysis of infant mortality rates published by Save the Children.