It's no secret that phthalates aren't good for a child's development. Previous studies have associated the class of chemicals to disruptions in the endocrine system as well as the reproductive system. But a new study may have found a direct link between a pregnant women's exposure to phthalates and negative impacts on her baby's development.

The study was conducted at Columbia University's Mailman School of Public Health and published this week in the journal Environmental Health Perspectives. Researchers measured levels of four kinds of phthalates in the urine of 319 non-smoking pregnant women that were part of an ongoing study involving women and their children. When the children reached 3 years old, they were evaluated for their mental, motor and behavioral development.

According to the study, phthalate exposure during pregnancy was associated with increased risk of motor delay and mental development — particularly in girls. Even after controlling for factors such as marital status, income level, and exposure to tobacco smoke, pesticides, or lead, researchers found the link remained. Robin Whyatt, a professor in the Mailman School of Public Health at Columbia University, and the lead author of the study commented, "As levels in the mothers' urine went up, the child's motor development went down significantly."

One of the phthalates evaluated was associated with "significant" decreases in mental development among girls, while three of the phthalates were significantly associated with behavioral disorders, or behavioral problems such as anxiety, depression, emotionally reactive behaviors and withdrawn behavior.

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