10.9.1: Infant Mortality

Infant mortality is defined as the death of an infant between the day they are born and 1 year old (NICHD, 2021). The most recent report from the National Center for Health Statistics (NCHS) shows an increase of 3% in the U.S. infant mortality rate between 2021 (19,928) and 2022 (20,538). Rates for infant mortality are typically expressed as the number of deaths per 1,000 live births. Racial disparities are also found with infant mortality rates, with the lowest rates in 2022 for infants of Asian (3.60) and White (4.52) and Hispanic mothers (4.88), followed by rates for infants of Native Hawaiian or Other Pacific Islander (8.50), American Indian/Alaskan Native (9.06), and Black mothers (10.86). The top five causes of death in infants are:

• congenital malformations
• premature birth and low birth weight
• sudden infant death syndrome (SIDS)
• unintentional injuries (accidents)
• maternal complications of pregnancy (Ely & Driscoll, 2023).

Exposure to toxins in the environment during fetal development can cause birth defects and potentially infant death. These toxins are referred to as teratogens. While some teratogens are well known, others have lesser known effects and are difficult to study due to the ethics of performing such research on pregnant people. Known teratogens include:

• Smoking, which can cause low birth weight,
• Alcohol consumption, which is linked to both physical and mental disabilities collectively called Fetal Alcohol Spectrum Disorders,
• Other drugs such as cocaine and heroin, which are associated with withdrawal symptoms after birth, and can cause impaired fetal growth, increase the risk of preterm birth and low birth weight, and are linked to learning disabilities and behavioral problems (Seabert et al., 2021),
• Radiation, which is associated with an increased risk for miscarriage, growth restriction, birth defects (including impaired brain function and malformations), as well as cancers (CDC, 2023c).

One of the most delicate systems during fetal development is the central nervous system (brain and spinal cord), which during the embryonic stage is called the “neural tube”. Supplementing with folic acid before and during pregnancy has been found to significantly reduce the risk of neural tube defects. The most common types of these birth defects are anencephaly and spina bifida. Anencephaly is an incomplete formation of the brain and skull, and typically causes death shortly after birth. Spina Bifida is a malformation of the spine which can cause paralysis or other physical disabilities. Anyone who can get pregnant or is intending to get pregnant is recommended to take prenatal supplements containing at least 400 micrograms of folic acid daily to prevent neural tube defects(CDC, 2022b). Two pivotal studies in the early 1990’s demonstrated a reduced neural tube defect risk of 72% or greater with folic acid supplementation, which prompted the FDA to require the addition of folic acid to enriched cereal products by the end of that decade. Adding folic acid to food sources increases health equity for those who may not be able to afford supplementation (Crider et al., 2022).

Infectious diseases such as syphilis and rubella can also have profound effects on a developing fetus. Congenital syphilis is passed through the placenta and can cause blindness and mental disabilities. Fortunately, syphilis is treatable with the antibiotic penicillin, even during pregnancy. Rubella is a virus which causes mild childhood illness but can cause deafness in a fetus if the mother contracts it during pregnancy. Rubella vaccines are typically part of childhood immunization schedules, and can prevent future deafness in offspring (Schneider, 2020). Lastly, toxoplasmosis is caused by a parasite that can be transmitted via eating undercooked, contaminated meat, or from indirect exposure to infected animals - particularly cats, through their feces. Although there might not be any symptoms present at birth, infants can develop severe brain and eye damage from congenital infection later on (CDC, 2022e). Zika virus is transmitted via mosquito bites, and although in adults it usually causes mild symptoms, infections during pregnancy can cause birth defects in about 5% of cases. Fetal transmission of Zika virus is associated with microcephaly - severely small infant head size at birth - and subsequent physical and mental disabilities such as difficulty feeding, seizures, and musculoskeletal issues (CDC, 2024i).

This image was captured during the 2016, Zika outbreak in Puerto Rico, by CDC staffer, Maureen Fonseca-Ford, who described the scene as follows, “While on deployment to Puerto Rico for the Zika response in May 2016, I led a focus group on the island of Vieques, where an unlikely group of low income, low literacy, young pregnant women, were some of the participants. They gave us some of the richest feedback, for improving the Zika communication materials in Puerto Rico. We have been working with the CDC Division of Vector-Borne Diseases (DVBD), and US-Mexico Unit (USMU), on creating effective, field tested materials, and this experience was one of the first times in CDC’s outbreak history, where behavioral science has been included at the outset of the response. This was a joint effort with Puerto Rico’s Department of Public Health.”