This is the second article of a five-part series about chemical exposure in pregnancy and childhood. For more context, start here.
Pregnancy is a unique time in a family’s life, both for the expecting parents and their growing baby. Researchers from the Maternal-Infant Research on Environmental Chemicals (MIREC) team are studying how environmental factors impact mothers throughout pregnancy and for the rest of their lives.
In 2007, Health Canada, along with academic and clinical research colleagues, launched Maternal-Infant Research on Environmental Chemicals (MIREC). 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.
Direction: conception
Even before the baby starts its journey in the womb, chemical exposures may impact how long it takes to get pregnant.
MIREC researchers measured hundreds of chemicals in MIREC mothers throughout pregnancy, to discover the role of bisphenol A (BPA), phthalates, triclosan, and perfluorinated substances on how long it takes to get pregnant.
“We found that patients with a higher concentration of PFOA, PFHxS and triclosan took longer to conceive,” says Dr. Maria Velez, Associate Professor in the Department of Obstetrics and Gynecology at Queen’s University and Principal Investigator for MIREC’s Kingston, Ontario site.
“Other studies revealed similar results for PFOA and PFHxS, but we were the first to study triclosan in this context.”
Complications of pregnancy
About 10 percent of pregnant women have gestational diabetes. This can introduce risks for mothers and babies, including increasing the likelihood of a caesarean birth, having a bigger baby, or the baby having high blood sugar levels at birth.
The MIREC team looked at the link between exposure to certain chemicals, such as toxic metals, plasticizers and phthalates, and the likelihood of developing gestational diabetes.
The most consistent association was with arsenic, which is found naturally in soils and groundwater, and we can be exposed to by consuming contaminated rice or water.
Over 80% of women had detectable concentrations of arsenic in their blood. Those women who had a higher arsenic concentration in their blood were three times more likely to develop gestational diabetes.
But more surprisingly, although arsenic did have a major impact on the risk for gestational diabetes on its own, mothers with male babies who are exposed to arsenic saw a further increase in the likelihood of gestational diabetes.
“I was really surprised by how much the sex of the fetus can impact its mother’s health. These factors can’t be considered separately, and it’s important to know the sex of the fetus to better understand the risks,” explains Dr. Robin Shutt, Senior Study Coordinator at Health Canada.
The importance of nutrition
The MIREC team was interested in looking at the importance of nutrition during pregnancy, more specifically, the impact vitamin D had on the mother and the baby.
In Canada, we have daily intake recommendations for vitamin D, but there is no specific recommended dose during pregnancy, like there are for folate.
Researchers looked at the different supplements that mothers were taking, and added sun exposure and food sources into their calculations. From there, they took and analyzed blood samples and were able to determine the vitamin D level for each woman, during early and late pregnancy and after delivery (postpartum).
“We learned that most mothers had an adequate level of vitamin D,” says Dr. Hope Weiler, Research Scientist in Health Canada Nutrition Research Division. “Of the modifiable factors that we looked at, supplements were the most important, among factors of variation in sun exposure and intensity, age, obesity, several chronic diseases and diet.”
Researchers also found that women with higher estimated vitamin D intake and calcium tended to have lower levels of certain metals like lead and mercury. This also extended to fetal cord blood, which confirmed that the fetus was also getting less exposure to these metals.
“Vitamin D seems to modify how our body reacts to metals in our environment. It’s hard to change our exposure to chemicals that are all around us,” says Dr. Mandy Fisher, Senior Epidemiologist at Health Canada. “But, we can modify our nutrition much more easily if we know that a supplement can help us get rid of metals in our system quickly.”
Vitamin D also plays an early role in bone health, especially for the prevention of rickets, which is a condition that affects bone development in children. “We know that congenital rickets still happens, so we want babies to be born with an adequate store of vitamin D, and to be able to sustain it through a supplement when they are breastfed,” explains Dr. Weiler.
It can also prevent complications in pregnancy, including gestational diabetes, preterm birth and babies that are small for their gestational age. There is also research looking at whether it could have an impact on the ability to conceive.
What’s next for pregnancy?
The MIREC team is planning to continue investigating the impact of metals such as mercury, lead, cadmium and arsenic on pregnancy. To date, researchers have found that even at the low levels at which Canadians are exposed, these metals could be linked to the risk of preeclampsia. In fact, arsenic has already been associated with hypertension in pregnancy.
Researchers now want to see how these chemicals impact not only gestational weight gain, but also the postpartum weight trajectory. They are following a sub-group of the MIREC participants and should have more results in 2022.
“It’s an area I’m really excited about. Postpartum women’s heath allows us to see how pregnancy and chemical exposure impact the women long term,” says Dr. Jillian Ashley-Martin, Research Scientist and Co-Principal Investigator of MIREC.
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: Exploring the impacts of environmental chemicals during pregnancy on unborn children.
Find out more:
Maternal-Infant Research on Environmental Chemicals (MIREC) Research Platform
- Link to previous MIREC blogs