Environmental chemicals may be obstacle for infertile couples

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George Duncan/flickr

By Lindsey Konkel
Environmental Health News
October 12, 2011

Kira Testin knew that something was wrong before she and her husband ever saw the fertility specialist. “We had been trying for a year to get pregnant,” recalls Testin, who was 27 at the time. “We weren’t naïve, but it still was devastating to hear that we would be unable to conceive naturally.”

For the Testins, in vitro fertilization (IVF) – when a woman’s eggs are retrieved, fertilized and grown to embryo-stage in a petri dish, then implanted back in her uterus – was their only chance at pregnancy.

And their chances were low at that. More often than not, IVF takes repeated, costly and heart-wrenching attempts.

Now scientists have found another potential obstacle for would-be parents. New research has turned up evidence of a link between endocrine-disrupting chemicals in the environment and poor IVF outcomes.

Some chemicals in food and consumer products may disrupt a woman’s estrogen, which interferes with her ability to get pregnant. Higher blood levels of pollutants such as bisphenol A (BPA), polychlorinated biphenyls (PCBs) and hexachlorobenzene (HCB) have been found in mothers with failed IVF attempts, according to a handful of recent studies.

The Testins, from a small town near Milwaukee, Wis., are among an estimated 9 million U.S. couples – one out of every eight – who are infertile, according to the American Fertility Association.

Causes of infertility are numerous, ranging from hormonal imbalances, to defects of the uterus, to misshapen sperm, low sperm count or low sperm motility in men.

Some scientists now theorize that endocrine-disrupting chemicals in the environment also can reduce fertility. Endocrine disruptors are a class of more than 1,200 chemicals that can mimic or block hormones, including estrogen, the primary female sex hormone involved in pregnancy.

“These chemicals may affect the way hormones regulate many aspects of our bodies, potentially even the ability to get pregnant,” said Laura Vandenberg, a reproductive scientist at Tufts University.

In one study of 765 women who underwent a total of 827 IVF cycles at Boston area clinics, researchers found an association between blood PCB concentrations and the rate at which embryos successfully attached or implanted to the uterine wall. The study was published in July in the journal Environmental Health Perspectives.

Endocrine-disrupting chemicals in the environment may affect the way hormones regulate many aspects of our bodies, potentially even the ability to get pregnant, say scientists. The odds of failed implantation doubled among women with the highest blood level of PCB-153 (the form of the chemical, on average, present in the highest concentration) compared to women with the lowest levels. Women with the highest levels were also 41 percent less likely to give birth to a live infant than women with the lowest blood levels.

Perhaps the most surprising finding – even low levels of PCBs, the same as those found in the general U.S. population, were associated with adverse early pregnancy outcomes in IVF, said Dr. Russ Hauser, professor of environmental and occupational epidemiology at Harvard School of Public Health and co-author of the study.

The same researchers also reported a link between another long-banned pollutant, hexachlorobenzene (HCB), and implantation failure, in a paper published online in Environmental Health Perspectives in August.

PCBs and HCB are both long-lived pollutants that accumulate in food chains and take decades to break down. Animal studies have shown that both types of compounds can mimic or block hormones. Hauser said there is evidence that HCB suppresses a hormone called luteal progesterone, which is important for egg implantation.

PCBs – a class of industrial chemicals used mostly as insulating fluids for electrical equipment – have been banned in the United States as well as in most other developed countries for more than 30 years. However, because of their extensive use and long half-life, human exposure remains widespread. In fact, studies have shown that more than 95 percent of Americans older than 12 still have detectable levels of PCBs in their blood. Humans are exposed mainly through food.

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Wellcome Images/flickr

HCB, a pesticide that has been banned in the U.S. since1984, is still used in some other countries. It also may be created as an impurity in production of other pesticides and chemicals.

The researchers detected HCB in the blood of every woman in the study. But, those with the highest blood levels were 1.71 times more likely to experience a failed embryo implantation than those with the lowest levels. On average, women in the study had even slightly lower HCB blood concentrations than those measured in the general population.

“Taken together, these studies demonstrate that low levels of environmental exposure to these chemicals may adversely affect early IVF outcomes that are critical to getting pregnant and maintaining a healthy pregnancy,” Hauser said.

IVF provides a window into the earliest stages of pregnancy that aren’t usually observable in couples conceiving spontaneously. Implantation failure, for instance, occurs before a woman even knows she’s pregnant.

Michael S. Bloom, a reproductive and environmental epidemiologist at the University at Albany-State University of New York, said BPA, which is found in some hard plastic beverage containers, paper receipts and food can linings, is another chemical that may interfere with egg development during IVF.

“In the case of BPA, we suspect that it may be interfering with the process by which human ovaries synthesize estrogen,” said Bloom.

Bloom and colleagues measured BPA concentrations in the blood of 44 women undergoing IVF at the University of California, San Francisco Center for Reproductive Health. They found that women with higher concentrations of BPA had lower peaks of estradiol, a form of estrogen important in the development of eggs in the ovaries.

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aa o'carroll/flickr

During an IVF cycle, a woman receives fertility drugs that stimulate ovarian cells in the follicle. As a result, the follicle, which contains the ovarian cells and the egg, gets bigger, estrogen levels rise, and the egg matures. Multiple eggs are stimulated to develop at once (as opposed to just one egg in a natural ovulatory cycle). Once retrieved from the woman’s ovaries, the eggs are fertilized with sperm in a petri dish in hopes that one or more will grow into a viable embryo.

“Estradiol production is considered an important marker of egg and follicular health during IVF ovarian stimulation,” said Bloom.

A surprising finding in the studies showed that even low levels of PCBs, the same as those found in the general U.S. population, were associated with adverse early pregnancy outcomes in IVF.Though it’s unclear what effect, if any, BPA may have on egg quality during IVF, “there is mounting data that a key enzyme that helps convert testosterone to estrogen may be inhibited by BPA,” said Bloom. This could potentially harm the development of the egg in the follicle during IVF.

Study participants had blood levels of BPA similar to those recorded in pregnant women but higher than those typically seen in the general population, according to the study, which was published in the journal Fertility and Sterility last month.

While BPA did not affect the number of eggs retrieved, “it’s worrisome that any compound could decrease productivity of the ovarian cells,” said Dr. Fred Licciardi, a specialist in reproductive medicine and surgery at the New York University Fertility Center who was not involved in the study.

Nevertheless, it’s too soon to say whether BPA and other chemicals are a cause of infertility. Bloom said the studies suggest these chemicals may be interfering with the IVF process, making it even more difficult to get pregnant. But, he said, “more research must be done before we can generalize beyond couples undergoing IVF.”

Some couples are always going to have fertility issues – whether it’s genetics or age or injuries to the reproductive system, said Tracey Woodruff, a reproductive health scientist in the division of Maternal-Fetal Medicine at the University of California, San Francisco Medical Center who was not involved in the studies.

“It’s unclear yet whether these findings are unique to the IVF community, or if we are just seeing the tip of the iceberg of a problem that extends beyond this population,” said Woodruff.

Only 41 percent of IVF cycles result in live births in women younger than 35, according to the Society for Assisted Reproductive Technology.

Women can take steps to reduce exposure to certain endocrine-disrupting chemicals. For instance, avoiding canned foods and disposable water bottles and buying BPA-free plastics, can reduce exposure to BPA. Other compounds, such as PCBs, accumulate in animal and fish fats.

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Tau Zero/flickr

But “these chemicals are so ubiquitous in the environment, it’s impossible to avoid them 100 percent,” said Vandenberg, the reproductive scientist from Tufts.

“There’s a huge burden on consumers to try to navigate through the grocery store, the drug store, the hardware store in order to avoid exposure to chemicals that we can’t see and don’t know are there,” she said.

PCBs, used mostly as insulating fluids for electrical equipment, have been banned in the United States and other developed countries for more than 30 years. However, because of their extensive use and long half-life, human exposure remains widespread.This means an increased burden on parents who may already be under a great deal of financial and emotional stress.

“I’m the type of person who likes to have a time line and a plan,” says Sarah Shepherd of Lexington, Ky., who with her husband underwent IVF in 2008. “Something that you think should be between you and your husband – like getting to choose the size of your family – now involves you, your husband, your bank account, and what you can handle physically and emotionally.”

Shepherd and her husband got pregnant on their initial IVF attempt, after first trying other reproductive therapies. Their son was born in 2008. Shepherd estimates the total cost of their reproductive treatments at more than $20,000.

Kira Testin gave birth to twin boys in 2005, after becoming pregnant on her fourth IVF cycle.

“With each failure I felt more pressure, each time another one of my friends conceived naturally,” said Testin, who estimated her infertility treatment cost around $40,000. Neither Shepherd’s nor Testin’s insurance covered IVF.

Testin says she did not worry about being exposed to environmental chemicals while she was pregnant or attempting to become pregnant. “Our doctor never brought it up,” she said.

  

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Environmental chemicals may be obstacle for "test tube" babies, by Environmental Health News is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License.