Pregnant women warned of risk of miscarriage from tinned food.
Pregnant women have been warned to avoid canned foods, microwaved food and plastic water bottles left out in the sun after a study found certain chemicals can increase the risk of miscarriage by 80 per cent.
The same advice has been issued to men whose partners are trying to conceive, after research found similar compounds contained in the same products can damage male fertility.
Research on animals has previously suggested that the chemical bisphenol-A (BPA) could threaten foetal survival but until now there have been limited studies on humans.
The new findings from Stanford University, presented at the American Society for Reproductive Medicine's annual conference in Boston, suggest that high levels of contact with the chemical found in many plastics could dramatically increase the likelihood of miscarriage.
The scientists behind the study said that it was impossible to avoid all contact with the substance, which is used in plastic packaging, tinned products and cash register receipts, but recommending limiting the impact of exposure.
In particular, they advised pregnant women to avoid cooking or warming foods in plastic containers, as chemicals leak far more quickly at higher temperatures, and to avoid letting plastic bottles of drinks get warm in the sun.
The same advice was issued to men whose partners are trying to conceive, after separate research found that the presence of similar chemicals found in the same plastics appeared to reduce male fertility by 20 per cent.
Earlier this year the Royal College of Obstetricians and Gynaecologists issued advice that pregnant women should "play it safe" and try to limit exposure to many chemicals found in plastics, because they said it would take years to properly assess the risks of exposure.
The new study on 114 pregnant women found that those with the high concentrations of the compound in their blood were 80 per cent more likely than those with low or normal levels to suffer a miscarriage.
Lead author Dr Ruth Lathi, reproductive endocrinologist at Stanford University said: "This is important because miscarriage is a very common occurrence and human exposure to BPA is near-ubiquitous."
The group studied had a history of miscarriages and difficulties conceiving.
Such women should avoid contact with products containing BPA as far as possible, said Dr Lathi.
Other pregnant women should take basic steps to limit their exposure, she said.
"There are some simple things that people can do but it’s impossible to avoid it completely.
"Avoid anything that involves cooking or warming food in plastic as the chemicals leak out of plastic materials at a higher rate at higher temperatures."
Even shopping posed a risk, she suggested, because many cash register receipts are coded with resin containing BPA.
"Avoid canned food, avoid cooking or heating plastic and then avoid unnecessary cash register receipts. Those are simple things that don’t cost a lot of money and are easy to do," said Dr Lathi.
Between 15 and 20 per cent of pregnancies end in miscarriage. While the risk increases with age, scientists have struggled to identify other causal factors.
Researchers said it remained unclear why BPA appeared to have such an impact on miscarriage rates, and said further studies were urgently needed.
While those who were most likely to miscarry had the highest level of the chemical in their blood serum, it was possible that they had metabolised the substance differently, so it stayed in the body longer, they said.
The chemical has previously been found to carry small risks to child development, and has been banned in baby bottles by the EU.
Dr Linda Giudice, ASRM President, said that while some previous studies has examined the impact of chemicals on those with fertility problems, the findings suggested BPA could have negative effects on a far larger group of people.
She said: "These studies extend our observations to the general population and show that these chemicals are a cause for concern to all of us."
Dr Giudice said that one of the most important things to avoid was drinking from plastic bottles which had been allowed to get warm.
She said: "Don’t leave your water bottles in the car in the sun. Studies show that levels of BPA increase by about 1000-fold in the water of a bottle that has been sitting in the sun."
However, the Miscarriage Association said the study was too small to draw definite conclusions, and that more research was needed.
The second study presented in Boston found that high levels of a group of chemicals called phthalates, which are also produced during the manufacturing of plastic and found in many skin-care products, significantly reduced the chances of conception.
The research on 500 couples found that when men had high levels of the chemicals - which are thought to disrupt the hormones - there was a 20 per cent lower chance of pregnancy, within a 12 month period examined.
Yet the same chemicals had no impact on women trying to conceive, according to the study led by the US National Institute of Child Health and Human Development.