The researchers said they issued the warning for pregnant women and nursing mothers because fetuses and newborn babies are particularly susceptible to the potential harmful effects of acrylamide, a possible carcinogen. The results of the study were to be broadcast nationwide Tuesday evening on a German television news program.

The leader of the study, Prof. Fritz Soergel of the Institute for Biomedical and Pharmaceutical Research in Nuremberg, said that acrylamide is highly water-soluble. Therefore, fetuses and infants are more at risk than adults because of their generally higher body water levels. Furthermore, blood brain barriers in fetuses and newborn infants are not full developed, meaning that nerve-damaging acrylamide would be more likely to reach their young brains and cause damage.

Acrylamide first received global attention in April 2002 when Swedish researchers reported finding the chemical in fried and oven-baked foods, especially in potato chips and French fries. The findings were at first greeted with skepticism, but scientists in other nations have since produced similar results.

High levels of acrylamide have been found to cause cancer in rodents. Last September the US Food and Drug Administration ( news - web sites) announced a plan to reduce or eliminate concentrations of acrylamide in potato and cereal products.

In Germany in the last few months, the potential health threat from acrylamide has become a major national issue, with Soergel gaining a reputation as an expert.

Soergel recommends that nursing mothers cease eating all potato chips, French fries or other potatoes fried in oil at temperatures over 180 degrees centigrade at least until the newborn baby reaches two months old. He believes pregnant woman should limit acrylamide consumption to no more than 20 micrograms per day, which he says would be the equivalent of about 10 grams of potato chips.

In an interview with Reuters Health, Soergel described acrylamide as a neurotoxic agent that he believes can cause cancer in humans. Soergel said that he and two colleagues--Prof. Rainer Weissenbacher, of the University of Munich, and Prof. Edgar Schoemig, of the University of Cologne--conducted their study during the past six weeks.

They used mass spectrometry to measure levels of acrylamide in the bodies of pregnant women and in the placentas after they gave birth, and also in nursing mothers and their breast milk.

Soergel said that tests showed anywhere from 10% to 50% of the acrylamide levels found in pregnant women was transferred via blood through the placenta to the fetus.

In breast milk, test showed up to 18.8 micrograms per liter of acrylamide, he said, adding that if a newborn baby drinks slightly over half a liter per day it would be consuming nearly 10 micrograms of acrylamide.

Soergel told Reuters that his team tested breast milk from only two nursing mothers and from the placentas of three women after they gave birth. However, he insisted that despite the small sample, the research team's main findings--that acrylamide can pass from a woman to a fetus and to a newborn through breast milk--remain valid.

"We wanted to very quickly have an idea," he said. "There is no doubt about these findings. It is so clear. The basic results will not be contradicted."

That said, he did concede that with a larger sample in the future, researchers will be able to more accurately determine levels of acrylamide that can pass through the placenta or into breast milk.

Soergel emphasized that non-fried potatoes, such as baked or boiled, are extremely healthy and should not be avoided by pregnant woman or nursing mothers. Potatoes fried at temperatures "substantially lower" than 180 degrees centigrade would have only very low levels of acrylamide and would therefore be safe to eat, he said. When pressed what temperature would meet his "substantially lower" requirements, he said 140 degrees.

"What I want to avoid is that mothers avoid potatoes altogether," he said.