A new research has warned expectant mothers to avoid the popular sweets during pregnancy, especially liquorice.

Eating lots of liquorice all-sorts while carrying a child can affect their IQ, affect their memory and increase their chances of ADHD, scientists discovered.

Experts are unsure if there is a safe limit of glycyrrhizin - found in liquorice - for pregnant women due to its harmful effects.  

Finnish researchers compared 378 youths whose mothers had either consumed large amounts or next-to-no liquorice while pregnant.

They defined a large amount as more than 500mg of glycyrrhizin each week - the equivalent to 250g of liquorice. 

In real terms, that is slightly more than a standard packet of Maynards Bassetts Liquorice Allsorts - which weigh 190g.

In the study, youths were then asked to perform cognitive reasoning tests to measure their intelligence levels.

They found those exposed to large amounts of liquorice in the womb performed less well. On average the difference was seven IQ points.

While it also made the youngsters have worse memory, according to the study published in the American Journal of Epidemiology.

Glycyrrhizin intensifies the effects of stress hormone cortisol by inhibiting the enzyme that inactivates cortisol. 

While cortisol is essential to the development of a fetus, it is detrimental in large amounts.

And parental estimates even suggested that the natural sweetener even caused ADHD-type problems.

While in terms of puberty, it was found to make girls start theirs earlier - putting them at risk of breast cancer, diabetes and heart disease.