Birth defects result from a combination of genetic, environmental, and behavioral factors. For the majority of birth defects, it is unclear how these factors work together or what the specific cause is. The rate of birth defects is not the same for every population. Disparities in birth defects can sometimes provide clues regarding the causes of disease. Perhaps more importantly, they enable us to understand the patterns of health outcomes as social justice issues. Researchers are not certain why some groups have higher or lower rates of birth defects. Possible explanations include the effects of poverty and racism, environmental exposures, diet, unequal access to healthcare, unequal treatment in the health care system, and genetic factors.
Race and ethnicity
Pre-term birth rates are highest among Black infants, and pre-term birth increases the risk of birth defects. Rates of neural tube defects are significantly higher among Hispanic infants than among other racial and ethnic groups in the United States. After accounting for maternal age, Hispanic infants were more likely to have Down syndrome than other infants. Asian infants have been shown to be at higher risk for oral-facial clefts. Rates of hypospadias have been shown to be higher in Whites when compared to other racial/ethnic categories.
Maternal age has been shown to be a risk factor for some birth defects.
For example, the risk of having an infant with Down syndrome, in particular, increases with maternal age. At age 35, the risk is about 1 in 400, while at age 45, the risk is about 1 in 30. Some research also suggests that infants born to very young (teen) mothers may have a higher risk for gastroschisis.
Geography and environment
Environmental factors may contribute to geographic disparities in birth defects. For example, living near a hazardous waste site, living near high traffic areas, and obtaining drinking water from a source with high concentrations of disinfection byproducts all increase the risk of some types of birth defects.