Short answers, pulled from the story.
The infant mortality rate (IMR) is the number of deaths of infants under one year of age per 1,000 live births. It is calculated by dividing the number of children dying under one year of age by the number of live births during the year, then multiplying by 1,000. A study across 135 countries over 11 years found education levels and life expectancy are the leading national indicators of IMR.
The three main leading causes of infant mortality are conditions related to preterm birth, congenital anomalies, and sudden infant death syndrome (SIDS). Globally, 86% of infant deaths are caused by infections, premature births, complications during delivery, perinatal asphyxia, and birth injuries. In developing countries, malnutrition and infectious diseases such as pneumonia, diarrhea, and malaria are also primary drivers.
Based on 2013 estimates, Afghanistan had the highest infant mortality rate at 121.63 deaths per 1,000 live births. Monaco had the lowest rate at 1.80 per 1,000 live births, followed closely by Japan at 2.21, Bermuda at 2.47, Singapore at 2.65, and Sweden at 2.74.
Non-Hispanic Black women in the United States have an infant mortality rate of 11.3, more than double the 5.1 rate for white women. Research shows the disparity cannot be fully explained by socioeconomic factors, as Latino Americans with similar poverty rates have much lower IMR. Researchers including Tyan Parker Dominguez at the University of Southern California link the gap to elevated stress among Black women, which produces hormones that can trigger premature labor. Arline Geronimus at the University of Michigan calls this cumulative stress process "weathering."
The global under-five mortality rate dropped from 22.5% in 1950 to 4.5% in 2015. Over the same period, the infant mortality rate declined from 65 deaths per 1,000 live births to 29 per 1,000. In 1960, the world IMR stood at 126; by 2001 it had fallen to 57 according to the Save the Children State of the World's Mothers report.
Sudden infant death syndrome (SIDS) is the leading cause of death in infants aged one month to one year in the United States, accounting for a share of approximately 3,500 sleep-related infant deaths annually. Placing babies to sleep on their backs, promoted by the Back to Sleep campaign, lowered the SIDS death rate by 50%. Immunizations given according to recommended guidelines have also been shown to reduce the risk of SIDS by 50%.