INFANT AND CHILD MORTALITY

During the twentieth century almost all countries experienced decreases in child mortality rates. However, the timing and pace of the decline varied substantially. Sustained reductions in child mortality began in the nineteenth century in Europe, North America, and Japan and continued gradually throughout the twentieth century. Major declines in other parts of the world generally began only after World War II. Mortality reductions in Asia, Latin America, and Africa were usually much more rapid than they had been in countries that began mortality declines earlier. By 1999 there were great variations in child mortality among countries. For example, although fewer than 0.5 percent of children died before the fifth birthday in Iceland, more than 33 percent died by age five in Niger.

Since the 1960s the decline in child mortality sometimes has appeared to have stagnated. One such period was 1975–1985, when many poor countries experienced severe debt crises and other problems, such as economic recovery from the oil crisis of 1973–1974. Recent evidence suggests that child mortality has continued to decline in most countries since 1980. However, during the 1990s the HIV/AIDS epidemic halted or reversed declines in child mortality in some eastern and southern African countries. For example, in Zimbabwe in the period 1990–1994 there were 80 deaths under age five per 1,000 live births. By 1999 that rate had increased to 118 deaths per 1,000 live births.

Measuring Infant and Child Mortality

Mortality rates often are calculated separately for the neonatal period (from birth to age 28 days) and the postneonatal period (from 1 to 11months of age). Infant mortality rates, which measure the probability of death in the first year of life, are the sum of neonatal and postneonatal mortality rates. The under-5 mortality rate (U5MR) refers to deaths from birth up to a child's fifth birthday. Each rate is calculated as the number of deaths in the specific age group per 1,000 live births. For example, a U5MR of 150 indicates that there are 150 deaths before the fifth birthday for every 1,000 live births, or that 15 percent of children die before age five. Estimates of infant and child mortality rates for every country are produced regularly by the United Nations Population Division.

Causes of Death and Morbidity

Causes of death vary substantially by age during the first five years of life. Deaths in the neonatal period are likely to be caused by "endogenous" conditions such as congenital malformations, chromosomal abnormalities, and complications of delivery, as well as by low birthweight. Deaths during the postneonatal period and between ages one and four years are likely to be caused by "exogenous," or external, factors such as infectious disease, accidents, and injury. As mortality rates decline, both postneonatal mortality rates and rates for one-to four-year-olds decline more rapidly than does neonatal mortality. The reason for this is that improved living standards, better health care, and public health programs have greater effects on exogenous causes of death than on endogenous causes.

As mortality rates decline, deaths under age five typically become more concentrated in the neonatal period until the infant mortality rate reaches about 20 deaths per 1,000 live births. With further reductions in infant mortality below this level this pattern generally reverses and child deaths become less clustered in the neonatal period as better prenatal, delivery, and postnatal care reduce mortality in the first month of life.

The leading causes of death for young children vary considerably, depending on the overall level of mortality. In countries with higher mortality rates infectious and parasitic diseases, especially acute respiratory infections (ARIs) and diarrheal disease, are the most important causes of death after the first month of life. In 1995 more than 50 percent of deaths among children under age five in poorer countries were due to ARIs, diarrhea, measles, or malaria. In low-mortality countries such as the United States the primary causes of death under age five are generally accidents, injuries, and perinatal conditions. In 1999 the leading causes of death in the United States were (1) in the neonatal period, congenital malformations and chromosomal abnormalities and complications of delivery, low birthweight, and a short gestation, (2) in the postneonatal period, sudden infant death syndrome (SIDS), congenital malformations and chromosomal abnormalities, accidents, and circulatory diseases, and (3) for one-to four-year-olds, accidents, congenital malformations and chromosomal abnormalities, cancers, homicide, and heart disease. In the year 2000 the cause-of-death structure in poor countries, in which infectious diseases are still a major cause of death, was very similar to that in the United States around 1900, when the U5MR was almost 200 deaths per 1,000 live births.

Reasons for Child Mortality Decline and Differential Child Mortality

The dramatic decline in mortality rates at all ages during the last 200 years in most human populations can be attributed to four broad causes: (1) increases in household income and associated improvements in nutrition, housing quality, and standards of living, (2) investments in public works (e.g., sanitation systems, garbage disposal, water quality, roads) and public health interventions (e.g., quarantines, mosquito eradication, vaccination), (3) changes in beliefs about disease causation and concomitant behavioral changes (e.g., hygiene, better treatment of illness), and (4) improvements in medical technology (e.g., pharmaceuticals, medical practices, vaccine development).

These factors all significantly reduced infant and child mortality and morbidity. Better living standards improved the diet of mothers and young children and reduced children's exposure to infectious organisms. Public works and public health programs further reduced exposure to infections and disease vectors (e.g., mosquitoes and other carriers), and vaccinations increased children's resistance to infection. Changes in beliefs about disease causation have substantially changed the way families and medical personnel care for infants and young children. For example, widespread knowledge that germs (e.g., bacteria and viruses) cause infectious diseases has led to improved hygiene particularly in food preparation for children, which has substantially reduced the prevalence of childhood diarrheal infections in low-mortality countries. Advances in medical technology have greatly improved the prevention and treatment of childhood illnesses, although this effect occurred mostly after World War II.

Extensive research has shown that socioeconomic status, particularly family income and maternal education, affects children's risk of illness and death. Poor, uneducated parents have more difficulty preventing their children from becoming ill and treating or seeking treatment for illness when it occurs. It has been suggested that socioeconomic status affects child health through five proximate determinants:

Maternal fertility patterns;
Environmental contamination;
Nutrient deficiency;
Personal illness control; and
Injury.

Certain maternal fertility patterns, including having children at very young (under 15 years) or very old (over 40 years) maternal ages, high parity (having had a large number of previous births), and having a child after a short time interval since the last birth (less than 24 months), appear to reduce children's survival chances, particularly when mothers are malnourished and high-quality prenatal and maternity care are not readily available.

Because infectious diseases are a major cause of child illness and death in high-mortality countries, environmental contamination in the household puts children at higher risk. Environmental contamination includes inadequate hand washing before food preparation and the feeding of children; contaminated water, clothing, and air; allowing children to put dirty objects in their mouths; and exposure to vectors of disease such as mosquitoes. Nutrient deficiency is important because malnutrition makes children more vulnerable to disease. Common types of malnutrition in poor children include inadequate caloric intake, protein-calorie malnutrition (inadequate caloric and protein intake), and micronutrient deficiencies (e.g., anemia and inadequate vitamin A intake). Breastfeeding provides an essential source of sanitary and complete nutrition for infants, particularly those who live in poverty. Personal illness control includes taking advantage of preventive measures such as immunizations, prenatal care, and malaria prophylaxis and treating illnesses promptly either through effective home remedies (such as oral rehydration therapy for the treatment of diarrhea) or by seeking help from medical personnel.

Sex Differences

In almost all populations mortality rates at all ages are lower for females than they are for males. Almost universally, girls have lower neonatal, postneonatal, and U5MR mortality rates than do boys. Research suggests that the differences are due to female genetic and biological advantages over males (Perls and Fretts 1998). Nonetheless, because the sex ratio at birth is generally about 105 male babies to 100 female babies, the number of boys in a population generally slightly exceeds the number of girls throughout childhood.

In a few cases, such as northern India, Pakistan, and Bangladesh, girls experience higher child mortality than do boys. Higher female child mortality also was observed historically in some European populations. This unusual pattern generally results from poorer care, less food, and less health care for girls than for boys. In these populations families coping with poverty may decide to invest their limited resources more heavily in sons, who are more likely to remain with the parents throughout their lives, than in daughters, who traditionally marry into other families at an early age.

The Role of Policy

Public policies have had both indirect and direct effects on child mortality and morbidity. Those with indirect effects include: (1) economic development policies that improved living standards and diet; (2) compulsory education, particularly for girls, which has changed the role of children in families and has led to higher levels of educational attainment for mothers; and (3) investments in transportation, communications, and public works projects, which have reduced the costs of transporting food, increased mobility and the diffusion of ideas and information, and provided clean water and sanitation.

International, national, local, and international agencies have attempted to improve child health directly through a wide array of programs and policies. For example, in the late 1800s and early 1900s New York and other American cities introduced milk stations where pasteurized milk was made available for children and eventually mandated commercial milk pasteurization. They also licensed midwives, implemented compulsory vaccination for schoolchildren, removed tuberculosis patients from their households, and provided widespread health education, including the promotion of breastfeeding.

Since World War II international agencies and national governments have coordinated efforts to improve children's health in African, Asian, and Latin American countries. These efforts have included improving access to health care, especially in rural areas; immunization campaigns; nutritional supplementation programs; and insecticide spraying to kill mosquitoes. In the 1980s international agencies and donors funded a series of child survival programs in low-income countries. Those programs were based on a set of "selected primary health care" measures that would have a substantial effect on child health but would not depend on the existing health care system in poor countries. Those efforts included child immunization programs, the distribution of oral rehydration packets, growth monitoring for children to detect malnutrition, and education programs to encourage breastfeeding. Some national programs also include nutritional supplementation for pregnant and breastfeeding women, malaria prophylaxis for pregnant women and children, and the distribution of "safe motherhood" kits.

An evaluation of these programs suggests that although immunization programs were often quite effective, some important causes of childhood illness and death, such as ARIs and diarrhea, cannot be reduced by selective primary health programs alone. Since the late 1990s the World Health Organization has been promoting a more comprehensive approach to improving child health in poor countries. Known as the Integrated Management of Childhood Illnesses (IMCI), this program includes three major elements: (1) improving the case management skills of health-care personnel, (2) improving overall health systems, and (3) improving family and community health practice. By June 2001 IMCI had been implemented in most Asian, Middle Eastern, and Latin American countries and in the countries of the former Soviet Union. Many African countries were also beginning implementation.