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Chemicals May Alter Placenta Genes

Researchers link endocrine disrupting chemical exposure to altered gene function in pregnant women’s placentas.

Researchers link endocrine disrupting chemical exposure to altered gene function in pregnant women's placentas, which could hamper fetal growth. (Image: Ultrasound image via Shutterstock)

Women exposed to widely used chemicals while pregnant are more likely to have altered gene function in their placentas, according to a new study.

It is the first study to show that exposure to phenols and phthalates may alter how genes are expressed in the placenta of pregnant women and suggests that such exposures may hamper fetuses’ proper development and growth.

“Altered expression of a gene is of concern because we will have more or less of a protein,” said senior author of the study, Karin Michels, a professor and epidemiologist at the Harvard Medical School and Brigham and Women’s Hospital in Boston, in an emailed response. “Proteins have essential function, for example, as hormones in the body.”

The researchers tested the urine of 179 women in their first trimester of pregnancy for eight phenols, including widely used bisphenol-A (BPA), and 11 phthalate metabolites, substances formed after the body processes phthalates. Then they tested how certain genes were expressed in the placenta. The women were enrolled in a study cohort at Harvard University.

They found that exposure was associated with altering certain molecules that regulate the expression of genes in the placenta. The study is concerning because the placenta is a lifeline for the fetus and properly functioning genes are crucial for the health of both the placenta and the growing fetus.

“The placenta is vital for nutrient transport to the fetus, regulation of oxygen, transport of waste out of the fetal compartment … preventing infection,” said Jennifer Adibi, an assistant professor and epidemiologist at the University of Pittsburgh who studies how chemicals impact placentas and fetuses.

“In the early stages, the fetus doesn’t have a functional endocrine system, it does not produce the hormones it needs to develop, and the placenta actually provides those,” said Adibi, who was not involved in the study.

Phenols and phthalates are widely used. Phthalates are used in vinyl products, in cosmetic as fragrances and in other plastics to make them pliable.

Phenols have a wide variety of uses including plastic resins, pesticides, and cleaning and personal care products. One of the most common, BPA, is ubiquitous and used to make polycarbonate plastic and found in some food cans and paper receipts.

Both phthalates and phenols are found in most people and the compounds are endocrine disruptors, meaning they interfere with people’s hormones. Disrupted hormones can lead to numerous defects and diseases.

During pregnancy, various hormones rise to ensure that the fetus is carried to term. “Phthalates and phenols may interfere especially with these hormones by either mimicking their effect or blocking them,” Michels said.

The first trimester is a “critical window of exposure for implications in adverse health outcomes later in life,” Michels and colleagues wrote in the study published this month in the Environmental Health Perspectives journal.

Adibi said the study is more evidence that human placentas respond “very uniquely” to chemicals such as phthalates. “This kind of challenges that historical view of the placenta—that chemicals pass through it in a passive way and interact with the fetus directly,” she said.

The study had “numerous shortcomings,” according to a statement from the American Chemistry Council (ACC), which represents chemical manufacturers.

“This study does not provide enough information about the source of potential exposures and the study participants themselves to draw conclusions about the findings,” the statement said.

The ACC also pointed out that the study did not draw any conclusions about negative health effects associated with potential exposures, as the researchers did not find any associations between the expression of genes and birth weights or lengths.

However the altered gene expression may affect other aspects of long-term health such as metabolism or hormones, which may not directly impact birth weight or length but could manifest later in childhood or adult characteristics, Michels said.