ZUMA PRESS/NEWSCOM

Phthalates, which are used in plastics and beauty products, were measured in 85 pregnant women, and the distance between the anus and the penis was measured in their male babies. Those babies and toddlers who had the highest exposure to phthalates in the womb had the shortest anogenital distance when adjusted for weight--the anogenital index (AGI). They also had smaller penises and more instances of undescended testicles.

"In rodents, the AGI is a sensitive measure of demasculinization of the male reproductive tract," says lead author Shanna H. Swan, professor of obstetrics and gynecology at the University of Rochester School of Medicine & Dentistry. As rodent pups mature, reduced AGIs develop into decreased sperm counts and lower testestorone levels, she says.

Researchers suspect that human babies with low AGIs will have reproductive problems when they mature because reproductive hormones in humans are very similar to those in rodents. They would like to see Swan's study repeated on a larger population.

The study could have implications for regulation of phthalates in the U.S. Many cosmetic companies that market in the U.S. have already agreed to remove some phthalates from their products.

The American Chemistry Council's Phthalate Esters Panel will follow this ongoing study with interest, Panel Manager Marian Stanley says. "As of now, the authors have yet to demonstrate that their data are solid or that they are meaningful."