Picture for illustrative purpose only. Image Credit: Gulf News Archive

London: Children who are bad at maths could blame their mother, a study suggests.

Five-year-olds who had been exposed to low levels of thyroid hormones while still in the womb were almost twice as likely to do badly in arithmetic tests as those whose mothers had normal levels, researchers found. Low thyroid levels can be caused by a shortage of iron, a common feature of pregnancy.

Pregnant women undergo regular blood tests to check their levels, and are advised to eat plenty of lean meat, green leafy vegetables and dried fruit and nuts to avoid problems. Some are advised to take supplements. Low levels of the hormone are also more common in those with a family history of the disease, and among those with other health problems, such as anaemia and type 1 diabetes, and among those with a family history of thyroid conditions.

Researchers from the VU University Medical Centre in Holland studied almost 1,200 children from birth to age five, when they assessed their test scores for language and arithmetic. They also monitored the mothers’ hormone levels when they were 12 weeks pregnant. Youngsters born to mothers with low levels of thyroxine were found to have lower test scores in arithmetic but their language tests were not affected.

“Whether these problems persist into adulthood remains to be seen,” said Dr Martijn Finken, the lead author, whose findings were presented at European Society for Paediatric Endocrinology Annual Meeting in Dublin. “We will continue to follow these children to answer this next big question.”

An underactive thyroid, known as hypothyroidism, can cause problems in growth and development of children. Previous studies have found that undetected or inadequately treated hypothyroidism in mothers was associated with IQ changes in infants. The average IQ scores were about four points lower in the children of hypothyroid mothers than in children of normal mothers.

The children of hypothyroid mothers were also more likely to have difficulty in school. In adulthood, underactive thyroids can cause tiredness, sensitivity to the cold, weight gain, depression, pain and numbness.

About 1 woman in 50 and 1 man in 1,000 develops hypothyroidism at some stage in life. It can occur at any age, but is most common with increasing age, with symptoms usually occurring gradually. It can also occur as a side-effect from some medicines.

Some women develop thyroid imbalance during pregnancy, and others after having a baby. This usually happens about three to six months after the birth, and usually corrects itself after a few months.

The Telegraph Group Limited, London 2014