For the first time, scientists have shown that pregnant mothers exposed to high but common levels of a widely used ingredient in cosmetics, fragrances, plastics and paints can have baby boys with smaller genitals and incomplete testicular descent.
The paper, published today in the journal Environmental Health Perspectives, found that the more a mother was exposed to the chemicals, called phthalates (THAL-ates), the greater the chance her boy’s reproductive development would be harmed. Similar changes have led to decreased semen quality and fertility in rodents. “We’ll have to follow our children to see what the consequences are,” says lead researcher Shanna Swan, a professor of epidemiology at the University of Rochester (N.Y.) School of Medicine.
The changes described in the federally funded study were seen at phthalate levels found in one-quarter of the female population in the United States.
The study tested levels of four kinds of phthalates in the urine of pregnant women. Researchers later examined 134 of the baby boys between 2 and 30 months of age born to those women.
Scientists measured the location, size and descent of the testicles, the volume of the penises, and the distance between the anus and the base of the penis.
That measurement, called the anogenital distance or AGD, is a sensitive indicator of masculinization, Swan says.
Previous work had shown that prenatal phthalate exposure in rodents can critically affect male hormones, resulting in impaired testicular descent and smaller genital size. But the Swan study is the first one to look at its affects in humans.
While none of the boys showed clear malformation or disease, in the 25 percent of mothers with the highest levels of phthalate exposure, the odds that their sons would have a shorter than expected AGD increased 10 times.