Infant mortality

Infant mortality is defined as the number of infants who are born alive, but die before one year of age. The most common cause of infant mortality worldwide has traditionally been dehydration from diarrhea. Because of the success of spreading information about Oral Rehydration Solution (a mixture of salts, sugar, and water) to mothers around the world, the rate of children dying from dehydration has been decreasing and has become the second most common cause in the late 1990s. Currently the most common cause is pneumonia. Major causes of infant mortality in more developed countries include congenital malformation, infection and SIDS.

Infanticide, abuse, abandonment, and neglect may also contribute to infant mortality.

Related statistical categories:
 * Perinatal mortality only includes deaths between the foetal viability (28 weeks gestation) and the end of the 7th day after delivery.
 * Neonatal mortality only includes deaths in the first 28 days of life.
 * Post-neonatal death only includes deaths after 28 days of life but before one year.
 * Child mortality includes deaths within the first five years after birth.

Infant mortality rate (IMR) is the number of newborns dying under a year of age divided by the number of live births during the year. The infant mortality rate is also called the infant death rate. In past times, infant mortality claimed a considerable percentage of children born, but the rates have significantly declined in the West in modern times, 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.

The infant mortality rate is reported as number of live newborns dying under a year of age per 1,000 live births, so that IMRs from different countries can be compared. A good source for the most recent IMRs as well as under 5 mortality rates (U5MR) is the UNICEF publication 'The State of the World's Children' available at http://www.unicef.org/publications/index_18108.html. For example, the worst U5MR is 284 in Sierra Leone. (That is, 28% of all children born die before they turn 5 years old.) The 29 countries with the highest U5MRs are in Africa. The U5MR of the United States is 8, and there are 31 countries with lower U5MRs, although many of those use a less stringent definition of mortality than the US. Sweden's is among the lowest at 3.

Comparing infant mortality rates
The infant mortality rate correlates very strongly with and is among the best predictors of state failure. IMR is also a useful indicator of a country's level of health or development, and is a component of the physical quality of life index. But the method of calculating IMR often varies widely between countries based on the way they define a live birth. 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.

The exclusion of any high-risk infants from the denominator or numerator in reported IMRs can be problematic for comparisons. The United States counts an infant exhibiting any sign of life as alive, no matter the month of gestation or the size, but some other countries differ in these practices. For example, in Germany and Austria, fetal weight must reach one pound to be counted as a live birth, while in some other countries, including Switzerland, the baby must be at least 12 inches long. Both Belgium and France report babies as born lifeless if they are less than 26 weeks' gestation.

Another well-documented example also illustrates this problem. Historically, 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 7 days. Although such extremely premature infants typically accounted for only about 0.005 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. 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.

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 and 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.

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. The main cause of this is that 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.

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. World infant mortality rate declined from 198 in 1960 to 83 in 2001.

However, IMR remained 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 Least 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.

Infant mortality rate in 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 The World Factbook's 2007 estimates) are shown below.