To use over-the-counter herbals during pregnancy is crazy

Dr Ann Walker University of Reading

Further studies showed that these women had been taking Ginkgo biloba, which is normally used to treat Alzheimer's and memory loss in older people.

Dr Petty said his team had only tested one type of Ginko biloba supplement, but declined to say which brand.

"It would be premature to generalise this to all manufacturers," but he said the problem could apply to other herbal medicines.

"Such supplements should be avoided by women who are pregnant or trying to conceive," said the report.

A spokeswoman for Britain's Royal College of Midwives said women must never assume that because remedies are "traditional" that they are necessarily safe.

Extreme care

Dr Ann Walker, senior lecturer in human nutrition at the University of Reading and a registered medical herbalist, said pregnant women should take extreme care about what they put into their bodies.

"To use over-the-counter herbals during pregnancy is crazy.

"The rule is that women should never take anything during pregnancy unless it is absolutely necessary.

"But I cannot see why most pregnant women would want to take this supplement unless they have circulatory problems. It is much more used by older people."

The report, from Chemical Research in Toxicology, is published in New Scientist.