Girls exposed to the chemical bisphenol A (BPA) while in the womb may be at increased risk for reproductive problems later in life, a new study in monkeys suggests.
In the study, female monkeys exposed to BPA in the womb were at higher risk for abnormal egg development compared with those not exposed to BPA. In female monkeys, as in humans, egg formation begins before birth.
However, it's not known whether BPA could have the same effect on egg development in people.
Additionally, because the monkeys in the study did not grow to reproductive age, it's not clear what effect the egg abnormalities could have on their ability to reproduce later in life. But the researchers speculated the abnormalities they observed could lead to an increased risk for miscarriages and birth defects, and a reduced "pool" of viable eggs.
"All the eggs that a female is going to have in her lifetime are formed before birth," said study researcher Catherine VandeVoort, a professor at the University of California, Davis. "Anything that disrupts that process is going to have an impact later in life," VandeVoort said.
The researchers said they hope to conduct a study in which monkeys exposed to BPA in the womb are followed into adulthood, to investigate whether they have problems conceiving healthy offspring, VandeVoort said.
BPA is found in many products, including canned foods, plastics, dental sealants and credit card receipts, so people are likely exposed to the chemical daily, the researchers said.
Previous studies in mice have suggested BPA exposure may be detrimental to egg development, but the researchers wanted to study the chemical's effects on monkeys because their reproductive system more closely resembles that of people.
The monkeys were exposed to BPA during pregnancy, either through their daily food during their second or third trimesters, or through an implant that provided a continuous, low dose of the chemical. The levels of BPA observed in the monkeys were similar to the levels seen in people, the researchers said. Monkeys in the control groups were not exposed to the chemical.
The fetuses exposed to the chemical daily through their mothers' food showed abnormalities — their egg cells showed signs that they would not divide properly during development. If this happens, egg cells will end up with too many chromosomes, which can lead to disorders such as Down Syndrome, or to miscarriage.
In addition, both groups of fetal monkeys exposed to BPA had problems with the formation of follicles, which are structures that surround the eggs as they develop. The fetuses exposed continuously to BPA had eggs that were not properly packaged into these follicles, the researchers said. This may mean that the egg would die before it matures, VandeVoort said.
Although similar findings have been seen in mice, the new results are important because "this is the closest we can get to humans," said Dr. Ana Soto, a professor of anatomy and cellular biology at Tufts University in Boston, who was not involved with the study. Studies that look at the link between fetal BPA exposure and reproductive problems in people would be difficult because of the long time that passes between birth and reproductive age, Soto said.
The new study will be published this week in the journal Proceedings of the National Academy of Sciences.
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