Air Pollutants Tied to Increased Risk of Birth Defects: Study

A California-based study has carefully monitored the impact of traffic-related air pollution and its affect on pregnant women.

According to the study, conducted by researchers from the Stanford University School of Medicine, pregnant women residing in cities who are exposed to traffic pollution in early pregnancy are at a higher risk of having children with serious birth defects.

For the study, researchers examined the data on quality of the air and birth defects of 806 women who resided in one of the smoggiest regions of the country - California's San Joaquin Valley - for the first eight weeks of their pregnancies between 1997- 2006. They compared the results with 849 women who gave birth to healthy babies in the same period. The first eight weeks is the window period when birth defects may develop.

The researchers examined two types of neural tube defects, cleft lip, with or without cleft palate, and cleft palate only. They also looked at kids with gastroschisis, a defect where infants are born with some of their intestines outside the body.

Based on the area the participant was living in, the researchers scored the subject's exposure to air pollutants using data collected by Environmental Protection Agency. They checked for carbon monoxide, nitrogen oxide, nitrogen dioxide, particulate matter, ozone and density of the local traffic.

According to Amy Padula, PhD, a postdoctoral scholar in pediatrics, there was a strong association between specific traffic-related air pollutants and neural tube.

"Birth defects affect one in every 33 babies, and about two-thirds of these defects are due to unknown causes," senior author of the paper Gary Shaw, PhD, professor of neonatal and developmental medicine, said in a press statement. "When these babies are born, they bring into a family's life an amazing number of questions, many of which we can't answer."

The researchers noticed that those women who inhaled the highest levels of carbon monoxide were twice as likely to give birth to an infant with spina bifida (a spinal column malformation) or anencephaly (underdeveloped or absent brain). On the other hand, women who were exposed to nitrogen dioxide were three times more likely to have a child with anencephaly.

The researchers plan to conduct further studies in order to examine the combined effect of multiple pollutants.

The result was published in the American Journal of Epidemiology.