(RxWiki News) Some jobs expose employees to a class of chemicals called chlorinated solvents, which are in many degreasers, cleaning products, paint thinners, pesticides, glues and similar products.
A group of researchers wanted to find out whether pregnant women who have likely been exposed to these solvents early in their pregnancy or around conception, might be more likely to have children with congenital heart defects.
"Avoid contact with chemicals - especially while pregnant."
The study was led by Suzanne M. Gilboa of the National Center on Birth Defects and Developmental Disabilities at the Centers for Disease Control and Prevention.
A total of 4,998 women were included in the study: 2,951 whose babies did not have congenital heart defects, and 2,047 women whose babies were born with a congenital heart defect.
The researchers looked for 15 different types of congenital heart defects in the babies and compared them to the estimated level of exposure that, via their mothers, the babies had likely had to a list of common organic solvents.
The estimations were determined by two methods, both based on data provided by the women in a questionnaire about her work experience from three months before conception through to the end of her pregnancy.
One method used experts in the field to estimate a pregnant woman's exposure to chemicals.
Two industrial hygienists reviewed all the data from the questionnaires and rated each job held by the women in terms of how much exposure she was likely to have to six different chlorinated solvents or to Stoddard solvent.
The chlorinated solvents they considered included carbon tetrachloride, chloroform, methylene chloride, perchloroethylene, 1,1,1-trichloroethane or trichloroethylene.
If there was a discrepancy between the two hygienists' estimates, it was resolved by a third hygienist, and none of them knew the information about the individual cases of the women or their other demographic data.
The second method relied on previously published data. The researchers reviewed the research literature and industry technical reports to estimate a person's exposure to those solvents in particular jobs.
The estimates were categorized in terms of the percentage of likely exposure: 0, 1 to 9 percent, 10 to 49 percent, 50 to 89 percent or 90 percent or greater.
"Exposure" for both methods was defined as working in a job with some level of exposure, for at least one month, during the time from three months before conception to the end of the first trimester.
Based on the estimates of the expert hygienists, about 4 percent of the mothers whose babies did not have birth defects had been exposed to an organic solvent around conception or the first trimester, compared to 5 percent of the mothers whose babies had heart defects.
Using the data estimates from published literature, both numbers doubled: 8 percent of women whose babies didn't have heart defects and 10 percent of women whose babies did were likely exposed to solvents during conception or first trimester.
The data using the expert approach was considered too close to show a significant association between the rate of birth defects and the women's exposure to solvents.
The results of the approach using published evidence of likely exposure was stronger in identifying a link between solvent exposure and congenital heart defects in the women's children.
The authors therefore concluded that it was possible that there was an overall association between women's exposure to solvents in the early part of her pregnancy and a higher risk of her baby having a heart defect at birth, but more research is necessary.
"Some of these findings were consistent with those previously reported in the literature, and other findings were new, yet all warrant corroboration in other study populations," they wrote. "Despite the strengths of this analysis, the results do not allow for the drawing of definitive conclusions on specific exposure-congenital heart defect combinations."
The study was published July 17 in the journal Occupational and Environmental Medicine. The research was funded by the Centers for Disease Control and Prevention, working with the Centers for Birth Defects Research and Prevention.
Funding also came from a grant from the National Institute for Occupational Safety and Health. The authors declared no conflicts of interest.