Infant mortality
Infant mortality is the death of an infant before the infant's first birthday. The occurrence of infant mortality in a population can be described by the infant mortality rate, which is the number of deaths of infants under one year of age per 1,000 live births. Similarly, the child mortality rate, also known as the under-five mortality rate, compares the death rate of children up to the age of five.
In 2013, the leading cause of infant mortality in the United States was birth defects. Other leading causes of infant mortality include birth asphyxia, pneumonia, neonatal infection, diarrhea, malaria, measles, malnutrition, term birth complications such as abnormal presentation of the fetus, umbilical cord prolapse, or prolonged labor. One of the most common preventable causes of infant mortality is smoking during pregnancy. Lack of prenatal care, alcohol consumption during pregnancy, and drug use also cause complications that may result in infant mortality. Many situational factors contribute to the infant mortality rate, such as the pregnant woman's level of education, environmental conditions, political infrastructure, and level of medical support. Improving sanitation, access to clean drinking water, immunization against infectious diseases, and other public health measures can help reduce rates of infant mortality.
In 1990, 8.8 million infants younger than one-year-old died globally out of 12.6 million child deaths under the age of five. More than 60% of the deaths of children under-five are seen as avoidable with low-cost measures such as continuous breastfeeding, vaccinations, and improved nutrition. The global under-five mortality rate in 1950 was 22.5%, which dropped to 4.5% in 2015. Over the same period, the infant mortality rate declined from 65 deaths per 1,000 live births to 29 deaths per 1,000. Globally, 5.4 million children died before their fifth birthday in 2017; by 2021 that number had dropped to 5 million children.
The child mortality rate was an indicator used to monitor progress towards the Fourth Goal of the Millennium Development Goals of the United Nations for the year 2015. A reduction in child mortality was established as a target in the Sustainable Development Goals—Goal Number 3: Ensure healthy lives and promote well-being for all at all ages., an analysis of 200 countries found 133 already meeting the SDG target, with 13 others trending towards meeting the target by 2030. Throughout the world, the infant mortality rate fluctuates drastically, and according to Biotechnology and Health Sciences, education and life expectancy in a country are the leading indicators of IMR. This study was conducted across 135 countries over the course of 11 years, with the continent of Africa having the highest infant mortality rate of any region studied, with 68 deaths per 1,000 live births.
Classification
Infant mortality rate is the number of deaths per 1,000 live births of children under one year of age. The rate for a given region is the number of children dying under one year of age, divided by the number of live births during the year, multiplied by 1,000.Forms of infant mortality:
- Perinatal mortality is late fetal death or death of a newborn up to one week postpartum.
- Neonatal mortality is death occurring within 28 days postpartum. Neonatal death is often attributed to inadequate access to basic medical care, during pregnancy and after delivery. This accounts for 40–60% of infant mortality in developing countries.
- Postneonatal mortality is the death of children aged 29 days to one year. The major contributors to postneonatal death are malnutrition, infectious disease, pregnancy complications, sudden infant death syndrome, and problems in the home environment.
Causes
Main causes
There are three main leading causes of infant mortality: conditions related to preterm birth, congenital anomalies, and SIDS. In North Carolina between 1980 and 1984, 37.5% of infant deaths were due to prematurity, congenital anomalies accounted for 17.4% and SIDS accounted for 12.9%.Premature birth
Premature, or preterm birth, is defined as birth before a gestational age of 37 weeks, as opposed to full term birth at 40 weeks. This can be further sub-divided in various ways, one being: "mild preterm, very preterm and extremely preterm ". A lower gestational age increases the risk of infant mortality.Between 1990 and 2010 prematurity was the second leading cause of worldwide mortality for neonates and children under the age of five. The overall PTB mortality rate in 2010 was 11.1% worldwide and was highest in low to middle-income countries in sub-Saharan Africa and south Asia, compared with high-income countries in Europe or the United States. Low-income countries also have limited resources to care for the needs of preterm infants, which increases the risk of infant mortality. The survival rate in these countries for infants born before 28 weeks of gestation is 10%, compared with a 90% survival rate in high-income countries. In the United States, the period from 1980 to 2000 saw a decrease in the total number of infant mortality cases, despite a significant increase in premature births.
Based on distinct clinical presentations, there are three main subgroups of preterm births: those that occur due to spontaneous premature labor, those that occur due to spontaneous membrane rupture, and those that are medically induced. Both spontaneous factors are viewed to be a result of similar causes; hence, two main classifications remain: spontaneous and medically induced causes. The risk of spontaneous PTB increases with "extremes of maternal age, short inter-pregnancy intervals, multiple gestations, assisted reproductive technology, prior PTB, family history, substance abuse, cigarette use, low maternal socioeconomic status, late or no prenatal care, low maternal prepregnancy weight, bacterial vaginosis, periodontal disease, and poor pregnancy weight gain." Medically induced preterm birth is often conducted when continuing pregnancy poses significant risks to the pregnant parent or fetus; the most common causes include preeclampsia, diabetes, maternal medical conditions, fetal distress, or developmental problems. Despite these risk factors, the underlying causes of premature infant death are often unknown, and approximately 65% of all cases are not associated with any known risk factor.
Infant mortality caused by premature birth is mainly attributed to developmental immaturity, which impacts multiple organ systems in the infant's body. The main body systems affected include the respiratory system, which may result in pulmonary hypoplasia, respiratory distress syndrome, bronchopulmonary dysplasia, and apnea. Other body systems that fully develop at a later gestational age include the gastrointestinal system, the skin, the immune system, the cardiovascular system, and the hematologic system. Poor development of these systems increases the risk of infant mortality.
Understanding the biological causes and predictors of PTB is important for identifying and preventing premature birth and infant mortality. While the exact mechanisms responsible for inducing premature birth are often unknown, many of the underlying risk factors are associated with inflammation. Approximately "80% of preterm births that occur at <1,000 g or at <28 to 30 weeks of gestation" have been associated with inflammation. Biomarkers of inflammation, including C-reactive protein, ferritin, various interleukins, chemokines, cytokines, defensins, and bacteria, have been shown to be associated with increased risks of infection or inflammation-related preterm birth. Biological fluids have been utilized to analyze these markers in hopes of understanding the pathology of preterm birth, but they are not always useful if not acquired at the appropriate gestational time-frame. For example, biomarkers such as fibronectin are accurate predictors of premature birth at over 24 weeks of gestation but have poor predictive values before then. Additionally, understanding the risks associated with different gestational ages is a helpful determiner of Gestational age-specific mortality.
Sudden infant death syndrome (SIDS)
Sudden infant death syndrome is defined as the sudden death of an infant less than one year of age with no cause detected after a thorough investigation. SIDS is more common in Western countries. The United States Centers for Disease Control and Prevention report SIDS to be the leading cause of death in infants aged one month to one year of life. Even though researchers are not sure what causes SIDS, they have found that putting babies to sleep on their backs, instead of their stomachs, lowers the risk. Campaigns like Back to Sleep have used this research to lower the SIDS death rate by 50%. Though the exact cause is unknown, the "triple-risk model" presents three factors that together may contribute to SIDS: smoking while pregnant, the age of the infant, and stress from conditions such as prone sleeping, co-sleeping, overheating, and covering of the face or head. In the early 1990s, it was argued that immunizations could contribute to an increased risk of SIDS; however, more recent support the idea that vaccinations reduce the risk of SIDS.In the United States, approximately 3,500 infant deaths are sleep-related, a category that includes SIDS. To reduce sleep-related infant deaths, the American Academy of Pediatrics recommends providing infants with safe-sleeping environments, breastfeeding, and immunizing according to the recommended immunization schedule. They recommend against the use of a pacifier and recommend avoiding exposure to smoke, alcohol, and illicit drugs during and after pregnancy.