Pregnant moms, keep away from that plastic shower curtain.

Ronda Kaysen: Baby boys who are exposed in the womb to chemicals in plastics are more "feminine" and less likely to play with typical boy toys, a study found.

Boys who are exposed to chemicals called phthalates are less likely to play with toys like cars, trains, and trucks, and they shy away from physical activities like roughhousing and wrestling. Phthalates, found in everything from PVC shower curtains to vinyl flooring, mimic the female hormone estrogen and suppress testosterone. In a previous study, the same researchers from the University of Rochester found that these chemicals can cause genital abnormalities in boys.

"We now know that phthalates, to which we are all constantly exposed, are extremely worrying from a health perspective, leading to disruption of male reproduction health and, it appears, male behavior too," Elizabeth Salter-Green, director of the chemicals campaign group CHEM Trust, told BBC News. "This feminizing capacity of phthalates makes them true 'gender benders.'"

This is just creepy. Now I can spend my days wondering if the reason my son doesn't like his new truck isn't because he's finicky, but because the apartment I lived in when I was pregnant had vinyl floors.

Ronda Kaysen is a freelance writer. Her work has appeared in the New York Times, Washington Post, BusinessWeek.com, Architectural Record, Huffington Post, New York Observer and AM New York. She lives in Brooklyn with her family.