Pregnancy iodine pills 'good for babies and economy
Recommending iodine supplements to all pregnant women could save the NHS money, say researchers.
A study in The Lancet concluded that if all pregnant women took a daily dose, it could boost children's IQ scores, causing health improvements.
Iodine is important for healthy brain development and there is some evidence that the UK population may not be getting enough.
But Public Health England (PHE) said a varied diet should offer enough iodine.
"The longstanding government advice is that everyone including pregnant women should be able to get all the iodine they need from a varied and balanced diet," said Dr Louis Levy, head of nutrition science, diet and obesity, at PHE.
Severe iodine deficiency has long been known to cause impaired neurodevelopment in unborn children.
But the picture is less clear in countries such as the UK where iodine intake may only be slightly below recommended levels.
The main source in the UK diet is milk but it can also be found in other types of dairy food, fish and - in smaller amounts - in some foods made from plants, such as cereals.
A previous UK study of around 1,000 pregnant women, published in 2013, found that around two-thirds could be classed as mildly to moderately deficient in iodine.
Lower levels of iodine during pregnancy were subsequently linked with slightly poorer IQ and reading scores when the children were eight years old.
Those 2013 findings sparked the latest study in which researchers calculated the potential impact of all women taking iodine supplements before conception, during pregnancy, and while they were breastfeeding.
They based the study on the assumption that around 67% of women do not get enough iodine from their diet, which is used by the body to make thyroid hormones.
Their estimates suggest that universal iodine supplements in pregnancy could boost children's IQ scores by an average of 1.22 points.
They then took evidence from other studies that had looked at economic benefits linked to IQ score.
Putting figures on the healthcare costs associated with different IQs - which had shown a higher IQ is associated with better health - into their model showed an average saving to the NHS of £199 per pregnant woman.
They also calculated, using previous research, that on average, the financial benefit for every pregnant woman taking the supplement would amount to £4,476 in higher earnings and lower education costs for her child.
The British Dietetic Association recommends that pregnant women need around 150mcg of Iodine more than other adults. Check if your pregnancy vitamin supplement tablets already provide this level. If not the best sources are White fish, Seafood and dairy products. Organic milk has less iodine than normal, and concentrated sources of iodine such as seaweed would provide too much extra iodine.