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Pregnant women’s sex hormones waver with phthalate exposure.
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Pregnant women’s sex hormones waver with phthalate exposure.

Women exposed to certain chemicals in flooring and food packaging early in pregnancy are more likely to have decreased free testosterone—hormones vital for fetal growth, according to a new study.

Women exposed to certain chemicals in flooring and food packaging early in pregnancy are more likely to have decreased free testosterone—hormones vital for fetal growth, according to a new study.


Estrogen and testosterone drive a fetus' genital development the first five to 18 weeks of a pregnancy. Altered levels of the sex hormones can lead to abnormalities in a baby's genitals. While the study doesn't prove phthalates in pregnant women lead to genital problems in babies, it suggests that the ubiquitous chemicals may impact fetal growth.

Researchers tested for evidence of phthalate chemicals in the urine of 591 women during their first trimester, from conception to 13 weeks. This window is the most important time for reproductive organ development in fetuses.

Women with higher levels of two types of phthalates had lower levels of free testosterone, according to the study published today in the Journal of Clinical Endocrinology & Metabolism.

Levels of free testosterone—the form of the hormone not bound to a protein in the blood—in the women were 12 percent lower for every 10-fold increase in the chemicals.

Free testosterone is important: Women with higher levels of free testosterone had a lower prevalence of baby boys with genital abnormalities, the authors reported. “Adequate testosterone concentrations are needed for normal male reproductive genital development."

“We need to ask ourselves if we are adequately protecting the public" when it comes to phthalates in consumer products, said lead author Dr. Sheela Sathyanarayana, an associate professor at the University of Washington Department of Pediatrics.

Most people have phthalates in their bodies as the chemicals are used widely in vinyl flooring, cosmetics, detergents, lubricants and food packages. The types of phthalates in this study were probably in dust or on food, rather than from cosmetics, Sathyanarayana said.

Researchers have previously found associations between phthalates and birth problems. In studies of rats, for example, when unborn males are exposed to phthalates in the womb it leads to reduced testosterone and genital defects such as hypospadias.

In humans, researchers have linked certain phthalates to a reduced distance between genitals and the anus, altered placental genes and miscarriages.

Despite growing evidence that phthalates are endocrine disruptors and can alter human hormones at low doses, they're still pumped into our goods: The U.S. Environmental Protection Agency estimates more than 470 million pounds of phthalates are produced each year.

Six types of phthalates are banned from kids' toys. The EPA, which regulates potentially harmful chemicals under the Toxic Substances Control Act, also requires manufacturers to notify the EPA if they're going to use a phthalate called DnPP in a product so the agency can deem if it's necessary.

One limit of the current study is that phthalates are so ubiquitous that body levels can swing rapidly in response to exposure. A single urine measurement may not be an accurate picture of the woman's exposure.

“Phthalate concentrations can change substantially with time of day and depending on what the subject has eaten recently," the authors wrote.

Karin Michels, professor and chair at UCLA's Department of Epidemiology, said the study also could have benefitted by testing the hormones in the cord blood of the babies.

She said pregnant women's hormones are already vacillating and that free testosterone is pretty low to begin with.

The women in the study are part of a group called The Infant Development and the Environment Study, which researchers are using to study how common chemicals affect pregnancy and birth outcomes.

The mothers were from one of four clinical centers: the University of California, San Francisco, the University of Minnesota, the University of Rochester Medical Center, or the Seattle Children's Hospital/University of Washington.

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