Clothing dye raises diabetes risk in pregnant women

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Pregnant women exposed to a harmful clothing dye have a higher risk for gestational diabetes when they are carrying a male fetus, according to a new study. 

Gestational diabetes, which afflicts roughly 8% of pregnant women in the US each year, increases the odds of a baby being born too large and suffering from low blood sugar, obesity and diabetes. 

The study, published Sunday in the Journal of Exposure Science and Environmental Epidemiology, is the first to link o-anisidine, an aromatic amine chemical commonly used in clothing dyes, to gestational diabetes.

“The clothes people wear shouldn’t come with this hidden risk to their health,” said Emily Lasher, lead author of the study and science associate at the University of California San Francisco’s Program on Reproductive Health and the Environment (PRHE). 

The study also found links between the chemical melamine, used to make plastic utensils and other products, and gestational diabetes, and it builds on previous evidence that stress can play a  key role in pregnant women’s health, finding that women who reported experiencing discrimination or other types of stress factors also faced higher risks for developing diabetes during pregnancy. 

Chemicals, stress and discrimination 

Researchers tested the urine of 607 pregnant women — 90 of whom developed gestational diabetes —  in the San Francisco region for 36 aromatic amines, which are found in clothes and hair dyes, pesticides, rubber products and tobacco smoke, and for melamine, which is used in some plastics, adhesives and kitchenware. They found eight of the compounds in about 65% of the samples, with melamine and cyanuric acid — a breakdown compound of melamine — in every sample.

“The clothes people wear shouldn’t come with this hidden risk to their health.” Emily Lasher, PRHE 

The strongest finding was among women carrying male fetuses who had higher levels of o-anisidine, which was linked to an 18% increase in gestational diabetes cases. Melamine and its breakdown compounds were linked to an 8% increase. 

The link to male babies aligns with previous research that found women carrying male fetuses are more likely to have poorer function in pancreatic cells that produce insulin. It’s not clear how the compounds may contribute to gestational diabetes, but melamine and aromatic amines have previously been found to cause inflammation, oxidative stress, cell damage and hormone disruption — all of which could contribute to insulin resistance. 

Beyond gestational diabetes, the compounds may directly harm babies. In animal studies, fetal exposure to melamine and aromatic amines is associated with development and reproductive problems. The compounds are also linked to cancer.  

The primary exposure to o-anisidine is through clothing, Lasher said. She said avoiding these chemicals is challenging because of widespread use. 

She recommended washing new clothes before wearing them, looking for certification for clothes that test for “azo-dyes” (which would cover o-anisidine) and avoiding cheap and brightly colored clothing, which would be more likely to contain the chemical.

Not regulated 

The EPA does not regulate the chemical outside of workplace exposure guidelines. 

“It’s not routinely biomonitored, we know it’s a possible carcinogen, and now we found a non-cancer health harm in gestational diabetes,” Lasher said. 

While melamine is used to make plastic forks, spoons and knives, plates and other plastic and paper products, the US Food and Drug Administration (FDA) does not allow it to be added to food or animal feeds. The agency says that it does not migrate from utensils and tableware at levels that would harm human health, unless they’re heated to “extreme temperature” — exceeding 160 degrees Fahrenheit — warning that “foods and drinks should not be heated on melamine-based dinnerware in microwave ovens.” 

Rashmi Joglekar, associate director of science, policy and engagement at PRHE, said the current political environment is a “perfect storm” for people’s exposure to chemicals like these. 

“The Trump administration is cutting funding for research like this, while trying to dismantle agencies that provide funding and could regulate this chemical,” she said. 

Stress and discrimination 

The links between stress and discrimination and gestational diabetes were even stronger: women with higher reported perceived stress and discrimination had 41% and 133% increased odds, respectively, of having gestational diabetes. 

Stress and discrimination could increase production of the stress hormone cortisol, which would impact pancreatic cells,” Lasher said. “And then there’s the theory that if you’re very stressed, you’re getting less physical activity, maybe you have an unhealthy diet.” 

Many scientists have recognized a link between stress and gestational diabetes, and a 2021 research review  confirmed that anxiety and depression increased the risk of a person developing gestational diabetes.

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