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).
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, andElizabeth 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.
“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 neurodevelopmentof children is ill advised,” they wrote. “Nor should unmonitored and adventitious dietary iodine sources continue to be relied on.”
Source: Endocrine Today
Effect of inadequate iodine status in UK pregnant women on cognitive outcomes in their children: results from the Avon Longitudinal Study of Parents and Children (ALSPAC)
As a component of thyroid hormones, iodine is essential for fetal brain development. Although the UK has long been considered iodine replete, increasing evidence suggests that it might now be mildly iodine deficient. We assessed whether mild iodine deficiency during early pregnancy was associated with an adverse effect on child cognitive development.
We analysed mother—child pairs from the Avon Longitudinal Study of Parents and Children (ALSPAC) cohort by measuring urinary iodine concentration (and creatinine to correct for urine volume) in stored samples from 1040 first-trimester pregnant women. We selected women on the basis of a singleton pregnancy and availability of both a urine sample from the first trimester (defined as ≤13 weeks’ gestation; median 10 weeks [IQR 9—12]) and a measure of intelligence quotient (IQ) in the offspring at age 8 years. Women’s results for iodine-to-creatinine ratio were dichotomised to less than 150 μg/g or 150 μg/g or more on the basis of WHO criteria for iodine deficiency or sufficiency in pregnancy. We assessed the association between maternal iodine status and child IQ at age 8 years and reading ability at age 9 years. We included 21 socioeconomic, parental, and child factors as confounders.
The group was classified as having mild-to-moderate iodine deficiency on the basis of a median urinary iodine concentration of 91·1 μg/L (IQR 53·8—143; iodine-to-creatinine ratio 110 μg/g, IQR 74—170). After adjustment for confounders, children of women with an iodine-to-creatinine ratio of less than 150 μg/g were more likely to have scores in the lowest quartile for verbal IQ (odds ratio 1·58, 95% CI 1·09—2·30; p=0·02), reading accuracy (1·69, 1·15—2·49; p=0·007), and reading comprehension (1·54, 1·06—2·23; p=0·02) than were those of mothers with ratios of 150 μg/g or more. When the less than 150 μg/g group was subdivided, scores worsened ongoing from 150 μg/g or more, to 50—150 μg/g, to less than 50 μg/g.
Our results show the importance of adequate iodine status during early gestation and emphasise the risk that iodine deficiency can pose to the developing infant, even in a country classified as only mildly iodine deficient. Iodine deficiency in pregnant women in the UK should be treated as an important public health issue that needs attention.