It is not clear how many birth defects are related to environmental exposures such as chemicals, drugs, and radiation. Some endocrine-disrupting chemicals including polychlorinated biphenyls (PCBs), dioxins, and pesticides, have been linked to nervous system defects and developmental problems such as reduced muscle tone and response. More data is needed to make these connections clearer.
Living near a hazardous waste site has been identified as a possible risk factor for birth defects such as neural tube defects, which affect the developing brain and spinal cord.
Exposure to disinfection by-products in drinking water such as trihalomethanes (THM) may increase the risk of some types of birth defects that affect the brain and spinal cord, the urinary tract, and the heart.
Other environmental factors suspected to be associated with birth defects include arsenic, plastics, solvents, and mercury.
The baby's development may be more susceptible to environmental exposures during the first trimester. This is the most sensitive time in pregnancy, when the organs and limbs are formed.