Pollution and gene interactions may raise birth defect risks

About 1 in 33 babies are born with a birth defect. Spina bifida, a neural tube defect, which is one of the most common birth defects, affects about 4 in 10,000 – 1,500 babies are born with spina bifida each year in the U.S. Spina bifida occurs when the neural tube does not close completely during development and can have a significant effect on the physical and neurologic well-being of a child. Because of this, it is a leading cause of disability in children.

To help women have healthy pregnancies and babies, I investigate what causes birth defects like spina bifida. Evidence indicates multiple factors can increase the risk of spina bifida including the environment, genetics and nutrition. Spina bifida tends to run in families – after having one child with the condition or if one of the parents has the condition, there is a 4% chance that the next child will also be affected, suggesting that genes play a role. Studies also find that cigarette smoking, obesity and folic acid deficiency may make a woman more likely to have a baby with spina bifida, revealing the environment is also important. I am investigating how environmental exposures such as air pollution, in combination with additional factors like genes, may make a woman more likely to have a baby with a birth defect.

Since cigarette smoke and outdoor air pollution have similar components, it is possible that exposure to air pollution affects pregnant women the same way as cigarettes. Women are particularly vulnerable to the effects of air pollution when they are pregnant because of the changes that occur to carry and develop the fetus.

UCSF-PregAirPollution-Infographic

Indeed, my previous research found a link between air pollution and spina bifida– women exposed to high levels of outdoor air pollution (the chemicals carbon monoxide and nitrogen dioxide) were at higher risk of having a baby with spina bifida. Next, I wondered how mom’s genetic makeup might affect this risk. My recent paper was one of the first to investigate this question—how the combination of a mother’s genetic differences and air pollution exposure during early pregnancy may contribute to her risk of having a baby with spina bifida. We found that genetic differences could increase the risk– women exposed to high levels of air pollution (especially particulate matter) during early pregnancy and who had certain genetic differences had a higher likelihood of having a baby with spina bifida. Some of the genetic differences involved how the body reacts to environmental chemicals—suggesting that some people are more susceptible to the toxic effects of air pollutants because their body processes chemicals differently. My research has also found that chemicals are not the only stressors that can increase risks. My previous study found that women who were exposed to high levels of air pollution and lived in neighborhoods with more poverty (a socio-economic stressor) were more likely to have a baby with spina bifida.

Although we are at the early stages of investigating gene-environment combinations and socioeconomic factors, it is clear that the causes of birth defects may involve multiple factors. It is also apparent that air pollution and other environmental stressors contribute to risks, and that certain people may be more susceptible to these exposures. I plan to expand our research on gene-environment combinations and focus on additional environmental exposures including drinking water contaminants and specific air pollutants that are produced from traffic and fires. My research shows that we need to consider multiple factors, including genetics, that can put women and their babies more at risk from exposure to air pollution when we develop interventions and policies to reduce risks to debilitating birth defects. Policies need to incorporate the most current science on susceptibility to limit harmful environmental exposures and protect women and children’s health.


PadulaAmy Padula, PhD, is an Assistant Professor with the Program for Reproductive Health and the Environment in the Department of Obstetrics, Gynecology and Reproductive Sciences at the University of California, San Francisco. Her doctorate is in Epidemiology from the University of California Berkeley and her postdoctoral training was at Stanford University.  Her research has been on the effects of ambient air pollution during pregnancy on adverse birth outcomes including preterm birth, low birth weight and birth defects. The projects have expanded to evaluate social factors, comorbidities during pregnancy and gene-environment interactions. Dr. Padula has an K99/R00 Transition to Independence Award from the National Institute of Environmental Health Science and las year was named one of the 20 Pioneers under 40 in Environmental Public Health by the Collaborative on Health and the Environment.
Dr. Padula’s co-authors on the papers referenced in the post above include: Gary Shaw, Wei Yang, Suzan Carmichael, Fred Lurmann, Ira Tager, Katharine Hammond and Kathleen Schulz.