Researchers at the University of Rochester announced on Mar. 16 that they are studying whether natural biological changes during pregnancy help reduce a fetus’s exposure to mercury. The project will focus on how the maternal gut microbiome and physiological changes related to pregnancy may increase the body’s ability to eliminate methylmercury, a toxic form of mercury commonly found in fish, before it reaches the developing fetus.
The topic is important because prenatal exposure to mercury has long been a concern for fetal brain development, especially given that fish is both a source of mercury and key nutrients for pregnant people. Understanding how the body manages this exposure could lead to clearer dietary recommendations for expectant mothers.
Matt Rand, PhD, associate professor of Environmental Medicine and principal investigator of the study, said: “Much of environmental health research focuses on identifying risks. What excites us about this project is the opportunity to understand the body’s natural defenses. Namely, how pregnancy itself may help protect the fetus from environmental exposures like mercury.”
The research builds on decades of work by University of Rochester scientists, including findings from the Seychelles Child Development Study. This international program has followed families in Seychelles—a population that consumes about ten times more fish than people in the United States—and found no measurable harm to children’s neurodevelopment from prenatal mercury exposure through fish consumption.
Rand and his colleagues have preliminary evidence suggesting that pregnant women may eliminate mercury more efficiently later in pregnancy. Using advanced laser ablation mass spectrometry, they can analyze single strands of hair to track patterns of mercury exposure and elimination throughout pregnancy. Early results indicate that mercury may be cleared from the body more rapidly during the third trimester than earlier stages.
The team believes changes in the gut microbiome during pregnancy could enhance this process by converting methylmercury into forms more easily excreted by the body. Participants in the new study will provide stool samples early and late in pregnancy so researchers can monitor these microbiome shifts, as well as hair samples from mothers and newborns to reconstruct patterns of mercury transfer.
Loralei Thornburg, MD, professor of Obstetrics and Gynecology at University of Rochester and co-investigator on the study, said: “Pregnant patients often receive mixed messages about fish consumption. This research will help us better understand how the body handles mercury during pregnancy and may ultimately guide clearer recommendations that support both maternal nutrition and fetal health.”
As research continues, findings could influence public health guidance regarding fish consumption during pregnancy by clarifying potential natural protective mechanisms.
