Iodine deficiencies during pregnancy linked to lower IQ in offspring

Iodine deficiencies during pregnancy may have negative neurocognitive outcomes among offspring, according to findings by researchers in the United Kingdom that were published in The Lancet.

“Pregnant women and those planning a pregnancy should ensure adequate iodine intake; good dietary sources are milk, dairy products and fish. Women who avoid these foods and are seeking alternative iodine sources can consult the iodine fact sheet that we have developed, which is available on the websites of the University of Surrey and the British Dietetic Association. Kelp supplements should be avoided, as they may have excessive levels of iodine,” Sarah C. Bath, PhD, RD, of the department of nutritional sciences at the University of Surrey, said in a press release.

Bath and colleagues analyzed stored samples of urinary iodine concentrations from 1,040 first-trimester pregnant women, measures of IQ from the offspring aged 8 years and reading ability at age 9 years. The mother-child pairs were collected from the Avon Longitudinal Study of Parents and Children (ALSPAC).

The researchers defined mild-to-moderate iodine deficiency as a median urinary iodine concentration of 91.1 mcg/L (interquartile range [IQR], 53.8-143; iodine-to-creatinine ratio of 110 mcg/g; IQR, 74-170).

Alex Stagnaro-Green

After adjusting for 21 socioeconomic, parental and child factors as confounders, data indicated that children of women with an iodine-to-creatinine ratio of less than 150 mcg/g were more likely to have scores in the lowest quartile for verbal IQ (OR=1.58; 95% CI, 1.09-2.3), reading accuracy (OR=1.69; 95% CI, 1.15-2.49) and reading comprehension (OR=1.54; 95% CI, 1.06-2.23) vs. those of mothers with ratios of at least 150 mcg/g. Furthermore, scores continued to dwindle when the less than 150-mcg/g group was subdivided, researchers wrote.

In an accompanying commentary, Alex Stagnaro-Green, MD, MHPE, professor of medicine and obstetrics and gynecology at the George Washington University School of Medicine and Health Sciences, and Elizabeth N. Pearce, MD, associate professor of medicine at Boston University School of Medicine, wrote that this study, along with previous research, represents a call-to-action because of the documented link between iodine deficiency and poor neurocognitive outcomes.

Elizabeth N. Pearce

“Absence of a public health policy in the face of clear documentation of moderate iodine deficiency and strong evidence of its deleterious effect on the neurodevelopment of children is ill advised,” they wrote. “Nor should unmonitored and adventitious dietary iodine sources continue to be relied on.”

For more information:

Bath SC. Lancet. 2013;doi:10.1016/S0140-6736(13)60436-5.

Stagnaro-Green A. Lancet. 2013;doi: 10.1016/S0140-6736(13)60717-5.

Disclosure: The researchers report no relevant financial disclosures.