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What to Know About 'Forever Chemicals' if You're Pregnant
Sara Blixt avoided canned tuna – even though it was the food she craved. But tuna meant mercury, a potential threat to her unborn son.
When he was born, she managed to breastfeed for only three months. "I felt like crap," she said.
Three years later, Blixt learned that she and others in her town, Ronneby, Sweden, had extremely high levels of per- and polyfluoroalkyl substances, or PFAS, in their blood. The municipal water supply was contaminated by firefighting foam used on a military base for years.
Blixt had likely passed the PFAS to her children through pregnancy and breastfeeding, and again by mixing formula with tap water.
Today, Sara Blixt is grateful – her children are healthy. Yet research increasingly shows that for many others, PFAS may mean harm: Fetal exposure has been linked to a higher risk of birth defects, liver disease, language disorders, and cancer.
Mothers, too, may get pregnancy complications due to PFAS, research suggests – such as high blood pressure and preeclampsia, a serious condition responsible for over 10% of maternal deaths across the globe. And just like Blixt, they may have trouble breastfeeding, and throw in the towel sooner than they would like.
PFAS, also known as "forever chemicals," are a class of man-made compounds used in nonstick and waterproof products. They are everywhere: in makeup, cookware, parchment paper, microwaveable popcorn, and rain-proof clothing. We ingest them via contaminated tap water and foods like meat and fish, and we absorb them through the skin.
Our bodies can get rid of PFAS, but slowly: It takes three to five years for the levels of PFOS, a common type of PFAS, to go down by half. "Everyone carries a little bit of PFAS in them," said Tracey Woodruff, PhD, MPH, a reproductive health researcher at the University of California, San Francisco.
Dangers During Pregnancy
PFAS are bad news for everyone, but pregnancy is a particularly vulnerable time. "The fetus is going through a lot of important biological changes that can be interrupted, and that can influence the future baby's health," Woodruff said. For mothers, breasts change to prepare for breastfeeding, breathing rate increases, and blood volume expands.
PFAS get transferred to the fetus via the placenta, which provides oxygen and nutrients to the developing baby. "Some toxins sneak through because they're similar in shape and size to things that the fetus might need to grow," said Megan Romano, PhD, an epidemiologist at the Geisel School of Medicine at Dartmouth. PFAS structurally resemble fatty acids, she said, which could help explain "why they seem to cross the placenta more than some of the other persistent pollutants."
Studies show that depending on the type of PFAS, the fetus receives between 30% and 80% of the mother's blood levels. Over the course of pregnancy, PFAS accumulate in the placenta – so the mother's levels go down after birth. "When you expel the placenta, it takes out a whole bunch of PFAS," Woodruff said. That's good for subsequent children: Several studies have found that the amount of PFAS the baby receives lowers with each birth. (Blood loss during birth also helps clear PFAS from the mother's body.)
PFAS and Lower Birthweight
High prenatal exposure to PFOA, another type of PFAS, has been linked to lower birthweights – studies show reductions of up to 8.8 ounces in babies born to highly exposed mothers.
Low birthweight has been linked to childhood obesity. Romano saw this play out in her research in New Hampshire: Some children who had elevated PFAS exposure were born small, but grew faster than others over the next two to three years, crossing into obese territory. "There may be a metabolic setpoint where your body is like, 'OK, I need to be taking in calories and growing all the time because I'm small and I need to catch up.' And then that doesn't really turn off when you do catch up," Romano said.
Several theories could explain why PFAS may affect birthweight. Animal research shows that forever chemicals interfere with how the mother's body handles fats, which then affects the baby's liver. (Negative effects on liver metabolism have been found in human fetuses, too.) PFAS also throws off maternal blood circulation, potentially affecting the placenta, the baby's nutrition center. "More than likely, it's all of the above," Romano said.
More Dangers: Cancer, Immunity, Brain Development
The negative effects of PFAS don't end with birth. A 2024 Finnish study showed that if a mother has elevated blood levels of one type of PFAS (found, for example, in some low pile carpets), her children are at a higher risk of acute lymphoblastic leukemia, the most common childhood cancer. A June study found that children exposed to high PFAS levels in the womb have 17% higher risk of high blood pressure as teenagers.
Other research links prenatal PFAS exposure with weaker vaccination response, suggesting children's immune systems may not be working as well as they should. A 2025 study found that babies exposed to PFAS during pregnancy grow up to be infection-prone kids.
Brain development may be affected, too. In Denmark, parents of children who came into contact with PFAS before birth reported more behavioral problems, from restlessness to temper tantrums. In Sweden, researchers found that highly exposed children from Ronneby were more likely to have a developmental language disorder. (This could mean limited vocabulary or challenges understanding spoken language.)
"Language development is a marker of general neural development," said Christel Nielsen, PhD, an epidemiologist at Lund University, Sweden, and one of the study's authors. "It could be a signal that this child might need more support to develop its full potential."
The Breast Milk Connection
Besides the placenta, PFAS can transfer to the infant through breast milk, although less efficiently, Nielsen said. In one study of Norwegian toddlers, the children's PFOS and PFOA levels increased by 3% to 5% per month of breastfeeding.
The milk itself may be less nutritious. Romano's recent study showed that breast milk from women exposed to PFAS contained more saturated fatty acids and n-6 fatty acids – not ideal. The milk also had lower levels of lactose. "On average, if there is a higher lactose content in the milk, it means that you're producing more," Romano said. This could explain why women who were exposed to PFAS during pregnancy are often unable to breastfeed for as long as they'd like.
But breastfeeding parents should not be discouraged, even if they were highly exposed to forever chemicals, both Romano and Nielsen agree. Breast milk boosts the immune system, helps the brain develop, and feeds the friendly gut microflora, potentially offsetting the negative impacts of PFAS.
So How Can You Avoid Forever Chemicals?
Dodging PFAS completely is tough, but you can reduce your exposure. Choose cookware made of "glass, cast iron, stainless steel, non-coated," Woodruff said. Eat fresh fruits and vegetables and fewer animal products – meat and fish contain more forever chemicals than do plants. Skip microwave popcorn – which combines PFAS (used in the bag lining) with high temperatures and fat for a particularly unhealthy mix.
PFAS can enter through the skin. So waterproof clothing and flame-retardant textiles can be sources. Go easy on makeup, especially foundation: In one study, people who usually wore it had over 50% higher levels of certain PFAS in their blood.
If you're pregnant, don't paint or remodel that baby room yourself: Some wallpaper, paint, and carpeting contain PFAS – although PFAS-free alternatives exist. "It's better to be safe than sorry," said Woodruff, whose team compiled a list of evidence-based tips.
How can you know if you've been highly exposed? There are U.S. and European water-contamination maps. Some jobs, like firefighters or workers who make or handle PFAS-containing materials, are linked to a higher risk. If you're concerned, you can ask your doctor for a PFAS blood test – though the cost can be high and access to the tests can vary.
One potential hope for those with high PFAS levels is a drug called cholestyramine, which has long been used for lowering cholesterol. Early studies suggest the drug helps the body recognize PFAS as a harmful substance and prevents it from being reabsorbed in the liver. A clinical trial found that it may decrease PFAS blood levels by 15% to 60%. The results are "promising," said Nielsen, and targeting highly exposed women before their first child "would be a top priority." But more research is needed before scientists can recommend the drug to the general population.
Above all, women shouldn't blame themselves for PFAS, Woodruff said. "This problem was made by the chemical manufacturing industry." What we now need is for the government to step in and regulate PFAS as a class, she said: Otherwise, we may drive ourselves crazy trying to figure out ways to avoid these chemicals. And the last thing parents-to-be need is more stress – which, by the way, is not best for the baby, either.
