Thursday, November 13, 2008; 12:00 AM
Bisphenol A (BPA) could hurt the chances of successful in vitro fertilization, or the ability of embryos to attach to the uterus, according to presentations at the American Society for Reproductive Medicine's annual meeting, which concluded Wednesday in San Francisco.
"The issue of environmental toxicants upon human reproduction is very important," said Dr. Richard J. Paulson, chief of the Division of Reproductive Endocrinology and Infertility at the University of Southern California Keck School of Medicine, who was not involved in the studies.
Last month, a U.S. Food and Drug Administration advisory panel said the agency had erred when it said that BPA, which is widely used in baby bottles and other plastic packaging for foods and beverages, posed no health risks. The agency said it would probably start research early in 2009 to determine the toxic effects of BPA on babies less than 1 month old.
In the first report, a team led by Dr. Julie Lamb, of the University of California, San Francisco, measured levels of BPA in people going through their first cycle of in vitro fertilization (IVF). Ninety-three percent of the 41 women had measurable BPA levels; among the 31 men, 81 percent had quantifiable levels of the chemical.
The researchers also found there was a small trend among women with measurable BPA levels not to become pregnant.
Paulson doesn't think this finding is proof that BPA can affect the chances of successful in vitro fertilization.
"Most of the women had detectable levels of BPA, indicating that BPA is definitely in the circulation of women undergoing fertility treatment," he said. "However, the significance of this finding is as yet uncertain."
In another presentation, Dr. Shelley Ehrlich of the Harvard School of Public Health and colleagues found that exposure to BPA did not affect semen quality. The researchers looked at BPA levels in the semen of 71 men and evaluated the quality of the semen.
Paulson said this finding was "reassuring, although the authors do caution that the study was small, and the results should be considered preliminary."
Commenting on these two studies, Dr. Hugh S. Taylor, director of the Division of Reproductive Endocrinology and Infertility at the Yale University School of Medicine, noted that the findings didn't reach the level of statistical significance.
"This is not where I suspected to find the defects related to BPA," Taylor said. "BPA seems more powerful as a developmental toxicant," he said, referring to fetal and early childhood development.
Exposure to BPA may prevent the embryo from attaching to the uterus, Aghajanova said.
Previous animal experiments have suggested that BPA may mimic the female sex hormone estrogen. The worry has been that exposure to the chemical can cause birth defects and developmental problems in children.
Exposure to BPA also has been suspected of causing a variety of other health problems, including cancer, diabetes, obesity and attention-deficit disorder. BPA exposure can occur through direct contact with the chemical or by exposure to food or drink that has been in contact with material containing BPA.
The Yale researchers have observed that when pregnant mice were exposed to BPA, the genetic chemistry of their female offspring is irreversibly altered. The researchers have the identified the gene in question as HOXA10, which regulates the normal development of the uterus and fertility, not only in mice, but also in humans. BPA sometimes plays havoc with the gene’s switching on and off. They can conceive but their ability to carry the pregnancy to full term is compromised, leading to permanent fertility loss