These include sugar added to food by manufacturers or found in products such as honey and fruit juice.
When comparing the 20 percent of mothers with the highest sugar intake versus the 20 percent of mothers with the lowest sugar intake, there was an increased risk of 38 per cent for allergy in the offspring (73 percent for allergy to two or more allergens) and 101 percent for allergic asthma.
"We can not say on the basis of these observations that a high intake of sugar by mothers in pregnancy is definitely causing allergy and allergic asthma in their offspring", said Professor Seif Shaheen from QMUL.
Scientists found children's risk of allergy-related chest problems soared in line with maternal intake of so-called "free" sugars.
Most importantly, the offspring's free sugar intake in early childhood was found to have no association with the outcomes seen in the analysis.
Medics think excess sugar sends a tot's immune system into overdrive - triggering inflammation in the lungs at a time when they are still developing. Taking too much sugar during pregnancy can double the chance of asthma in your kid. There was only a weak evidence that validates the link between sugar consumption and asthma risk overall.
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"We can not say on the basis of these observations that a high intake of sugar by mothers in pregnancy is definitely causing allergy and allergic asthma in their offspring", said lead researcher Seif Shaheen, Professor from QMUL.
'However, given the extremely high consumption of sugar in the West, we will certainly be investigating this hypothesis further with some urgency.
The study, published in the European Respiratory Journal, drew on data from the Avon Longitudinal Study of Parents and Children.
"In the meantime, we would recommend that pregnant women follow current guidelines and avoid excessive sugar consumption".
Dr Sheena Cruickshank, from the British Society for Immunology, said many factors influence a baby's allergy risk, including exposure to bugs and pollutants, and the type of milk the infant is fed.
Bedard and her colleagues examined the sugar consumption in mothers and compared it with asthma diagnosed and allergies in children at the age of 7 years.