Researchers led by the Centre for Research in Environmental Epidemiology (CREAL) in Barcelona found that junk food can have a damaging effect on the unborn baby, leading to them being born a far lower than average weight.
In fact, chips could be just as dangerous to an unborn baby as smoking, experts have cautioned.
Scientists have discovered that the culprit is a potentially deadly chemical called acrylamide which is found in home-cooked and processed foods including crisps, chips, bread and coffee, the Daily Express reported.
Acrylamide is a chemical which is produced naturally in food as a result of cooking starch-rich food at high temperatures, such as when baking or frying.
The study found that mothers-to-be who have a high intake of acrylamide are also more likely to have a baby which has a smaller head circumference.
The size of a child's head has been associated with delayed neurodevelopment while lower birth weights have been associated with adverse health effects in early life.
More From This Section
Babies born to mothers with a high dietary intake of acrylamide were found to be up to 132 grammes lighter than babies born to mothers who had a low intake.
The average birth weight among children who were exposed to the highest levels of acrylamide compared with children in the lowest was around 100 grammes.
The effect caused by acrylamide is comparable to lower birth weights caused by smoking when pregnant and the infant's heads were also up to 0.33 centimetres smaller.
"186 women from the Born in Bradford study took part in this major European research programme. We found that their babies had the highest levels of acrylamide out of all of the five centres, almost twice the level of the Danish babies," Dr Laura Hardie, reader in molecular epidemiology at the University of Leeds, said.
"When we investigated their diet it was clear that the largest source of dietary acrylamide is from chips," Hardie said.
Researchers examined the diets of 1,100 pregnant women between 2006 and 2010 in Denmark, England, Greece, Norway and Spain.
They used food-frequency questionnaires on mothers and also examined each baby's cord blood - which provides information about levels of acrylamide exposure during the last months of pregnancy.
"Reduced birth weight, in particular low birth weight, has been shown to be related to numerous adverse health effects early or later in life such as cardiovascular disease and diabetes. Furthermore, reduced birth head circumference has been associated with delayed neurodevelopment," lead author Dr Marie Pedersen said.