According to a policy statement from the American Academy of Pediatrics, all pregnant and breast-feeding women should take a supplement with adequate iodide. It turns out that many American women may be marginally iodine deficient, and studies estimate that only 15 to 20 percent of pregnant and nursing women are taking supplements containing iodine.
In the developing baby, iodine is necessary for thyroid function and normal brain development. According to a recent Lancet study, even children born to women with mild-to-moderate iodine deficiency during pregnancy are at increased risk for lower IQ and reading ability (assessed at age 9). The most severe effects were observed among children born to women with severe deficiency.
To reduce the risk of iodine deficiency, iodine was added to table salt. Nowadays, however, most salt consumed by Americans comes from processed foods which is prepared with salt that is not iodized. At greatest risk for iodine deficiency are women who are vegan (and others who do not consume dairy and fish); hence the need for supplementation.
Unfortunately, not all prenatal vitamins contain adequate amounts of iodine; you need to read the label carefully. It is recommended that pregnant and breastfeeding women should take a supplement that includes at least 150 micrograms of iodide, and use iodized table salt. Combined intake from food and supplements should be 290 to 1,100 micrograms a day.
Ruta Nonacs, MD PhD
Policy Statement: Iodine Deficiency, Pollutant Chemicals, and the Thyroid: New Information on an Old Problem. Pediatrics. 2014; 133:1163-1166.