Bringing baby home

This is the third article of a five-part series about chemical exposure in pregnancy and childhood. For more context, start here.

 

Why are some babies smaller than others while they are growing inside their mother, or have a lower birth weight?

 

Researchers from the Maternal-Infant Research on Environmental Chemicals (MIREC) are examining links between chemical exposure and how it may impact babies at birth.

MIREC is an ambitious, multi-year study of environmental chemicals and their possible health effects on mothers, starting during pregnancy and throughout childhood development, from infancy to adolescence.

Growing a human

When some babies are not growing in the womb as expected, medical professionals refer to them as being small for their gestational age, or SGA.

These babies are at a higher risk of being born prematurely, which carries its own set of risk factors.

The MIREC team has been trying to determine if there is a link between SGA babies and exposure to metals during pregnancy.

Through MIREC, researchers found that women with the highest levels of mercury in their blood were 50% more likely to have SGA babies.

Women who had higher levels of organic arsenic species (more specifically a chemical in the arsenic family called arsenobetane) in their blood—a compound mostly found in fish and considered to be non-toxic for humans—were also more likely to have SGA babies.

This information can help doctors and decision-makers provide better guidance to women to ensure they make informed dietary decisions that help their babies grow up healthy and strong.

Tiny hands and tiny feet

When babies are born weighing under 2,500g, they are considered small and may have trouble eating, gaining weight and fighting off infections.

Some may also have long-term health problems.

“We are surrounded by trace metals and precious metals, and they are not going away with the increasing use of electronics,” says Mandy Fisher, Senior Epidemiologist at Health Canada.

“Previous studies showed a link between some of these chemicals and low birth weight.”

Currently, researchers are also looking at the impact of PFAS, or per- and polyfluoroalkyl substances, commonly used in food and consumer products, on the birth weight of babies. More specifically, they examined the combined effect of three PFAS (namely PFOA, PFOS and PFHxS) on birth weight. They found that women with a higher exposure to PFOS had a higher chance of having a smaller baby, but that there was no impact from exposure to the other types.

What’s next?

The next step for this research will be to look at 60 different chemicals to see how they interact with each other and how they might affect a baby’s birth weight.

“This is an area that is really “hot" in environmental epidemiology,” explains Dr. Jillian Ashley-Martin, Research Scientist and Co-Principal Investigator of MIREC. “In order to truly understand their effects, we need to be able to monitor cumulative exposure of several chemicals.”

In the coming months and years, MIREC researchers intend to closely examine the impact of breastfeeding on children.

Although there is some research in this area already, there is a lot more to examine. Researchers will look at the content of breast milk, including chemicals, nutrients, and fungal toxins, to determine how this affects the baby.

This research will provide decision-makers with concrete information to provide the best possible advice to mothers.


The MIREC research is a key part of the Chemicals Management Plan. This plan seeks to reduce the risks posed by chemicals to Canadians and their environment by assessing chemicals used in Canada and by taking action on chemicals found to be harmful to human health and/or the environment.

Research like this provides information to decision-makers and can help guide their actions to change the future.

Stay tuned over the next few weeks for more articles about the MIREC studies throughout the different life stages of mothers and their children.

Up next: Examining chemical exposure in preschoolers.

Find out more:

Maternal-Infant Research on Environmental Chemicals (MIREC) Research Platform

MIREC Canada