Although polychlorinated biphenyls (PCBs) were banned decades ago, they are still pervasive in many countries and may contribute to failed in vitro fertilisation (IVF) attempts, a new study suggests.
In fact, PCBs may account for a 40% reduced chance of a live birth after IVF, the researchers said.
"These findings may help explain why these chemicals were associated with fertility issues in other studies," said lead researcher John Meeker, an assistant professor of environmental health sciences at the University of Michigan School of Public Health.
Meeker noted that there is not much women can do to avoid PCBs, since they are still found in seafood and dairy foods.
"Levels of PCBs have been declining gradually over the past couple of decades, but when or if these levels reach zero isn't known," he said. The report is published in the journal Environmental Health Perspectives.
PCBs and birth rates
For the study, Meeker's team collected data on IVF attempts of 765 women. In addition, they tested blood samples for 57 different PCBs.
Among these women, 286 gave birth, but 530 lost their babies, the researchers found. Of those who lost their baby, 229 had implantation failures and 301 had miscarriages.
Specifically, Meeker's group looked at blood levels of PCBs called congeners 118, 138 and 153, along with total PCB exposure.
They found that women with the highest levels of PCB 153 and total PCBs had twice the risk of implantation failure, compared with women with the lowest levels.
Moreover, women with the highest levels of these chemicals were 40% less likely to give birth, they added.
Meeker's team noted that these data may not apply to couples not using IVF, and may vary due to factors not accounted for in the woman's partner.
"PCBs may or may not affect IVF"
Commenting on the study, Dr George R. Attia, director of the division of reproductive endocrinology and infertility at the University of Miami Miller School of Medicine, said that "I'm not really convinced."
"This study did not show a cause-and-effect relationship between PCBs and these outcomes," he said. "We cannot say it doesn't, but neither can we say PCBs have a cause-and-effect relationship either."
Attia did not say women should not be concerned about PCB exposure, but studies that look for a cause-and-effect relationship are needed to prove the connection between these chemicals and adverse IVF outcomes, he explained.
Although PCBs, which were compounds used in industrial materials, were banned in the United States and other countries in the 1970s, they still persist due to widespread use and resistance to breakdown. Exposure to PCBs occurs mostly through foods and they have been linked with reproductive problems, Meeker said.
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