PROTECT Study finds further evidence that exposure to metals, phthalates, pesticides, among other chemicals contribute to negative birth outcomes such as miscarriage

A recent PROTECT study from Project 2 provides the scientific community with further evidence that exposure to chemicals such as metals (cadmium, arsenic, lead and chromium), phthalates (dibutyl phthalate, diethylhexyl phthalate), volatile organic compounds (trichloroethylene, carbon tetrachloride), pesticides (dieldrin, atrazine, parathion) and polycylic hydrocarbons (naphthalene) may be harmful during pregnancy and ultimately cause adverse birth outcomes. Exposure to these chemicals comes from a diverse set of sources including cigarette smoke, drinking water and plastic food packaging.

The team used publicly available data to investigate whether genes associated with miscarriage are turned on or turned off by exposure to environmental contaminants relevant to our Puerto Rico cohort. They discovered that several chemicals found in the environment which are known to affect a relatively high number of genes involved in miscarriage were also present in the blood and urine of pregnant women in Puerto Rico. This is important because exposures to chemicals that increase the risk of miscarriage, and thus decrease the likelihood of live birth, may have implications for studies of pregnant women and birth outcomes. “While further research is needed, such as on levels of exposure that lead to increased risk for miscarriage, this study highlights the need to consider exposure to these chemicals when studying the link between chemical exposures and adverse pregnancy outcomes,” explains first author Sean Harris.

In this study, the Comparative Toxicogenomics Database was used to help develop a unique statistical approach to look for links between chemicals and genes involved in miscarriage.  A statistical model was developed to conduct analysis since miscarriage is particularly challenging to model in laboratory animals or in cell and tissue cultures due to species differences and the general complexity of biological events involved. Additionally, there are many thousands of chemicals in the environment which make it impossible to thoroughly test them all for reproductive and developmental toxicity. These limitations cause the need for creative alternative methods such as the data mining approach that was used in this study. 

This publication provided important information about which chemical exposures may contribute to miscarriage risks in this population of pregnant women in Northern Puerto Rico. “When investigating the association between chemical exposures and preterm birth, chemicals that increase the risk of miscarriage may lead to a ‘live-birth bias’ in which the impact of these chemicals is not fully considered due to miscarried pregnancies being excluded from our analysis,” says Sean. “Thus, this study provided important insight into the impact of chemical contaminants on pregnancies in Puerto Rico, ultimately improving our ability to assess the impact these contaminants have on preterm birth rates.”