Iodine Supplementation for Pregnancy and Lactation—United States and Canada: Recommendations of the American Thyroid Association

Abstract

The fetus is totally dependent in early pregnancy on maternal thyroxine for normal brain development. Adequate maternal dietary intake of iodine during pregnancy is essential for maternal thyroxine production and later for thyroid function in the fetus. If iodine insufficiency leads to inadequate production of thyroid hormones and hypothyroidism during pregnancy, then irreversible fetal brain damage can result. In the United States, the median urinary iodine (UI) was 168 microg/L in 2001-2002, well within the range of normal established by the World Health Organization (WHO), but whereas the UI of pregnant women (173 microg/L; 95% CI 75-229 microg/L) was within the range recommended by WHO (150-249 microg/L), the lower 95% CI was less than 150 microg/L. Therefore, until additional physiologic data are available to make a better judgment, the American Thyroid Association recommends that women receive 150 microg iodine supplements daily during pregnancy and lactation and that all prenatal vitamin/mineral preparations contain 150 microg of iodine.

Iodine deficiency during pregnancy: a national cross-sectional survey in Latvia

“…The present study also indicates that the median IUC was significantly higher in the second and third trimesters, which could be attributed to the intake of iodinecontaining supplements. However, the intake of iodine Table 3 The association between dietary factors and participants' characteristics and logarithmically transformed UIC (μg/g Cr) in multiple linear regression analysis; nationally representative sample of pregnant women (n 683), Latvia, 2013 supplements containing 150 µg iodine, as recommended by the American Thyroid Association (29) , did not explain that association and also did not appear to be more effective in reducing the iodine deficiency during pregnancy. This might be attributed to the fact that in our study there was an insufficient number of women taking supplements containing ≥150 μg iodine to find the difference between subgroups statistically significant.…”

Autoimmune Thyroid Disease in Pregnancy: A Review

“…Interpretation of thyroid function tests should be trimester-specific, 28,47,48 and locally generated trimester-specific reference levels should be applied when available. 47,49 Of note, it has been reported that the upper 95% Cl for plasma TSH in the first trimester is 2.5 mU=L. 47 It is known that the TSH level descends 60%-80% by week 10 and recovers slowly thereafter, but it may not reach the preconception normal range until gestation ends.…”

“…During pregnancy and breastfeeding, women should increase their daily iodine intake to 250 mg daily. 46,49,59 LT 4 therapy is needed if, despite the iodine supplementation, abnormal serum TSH levels are detected.…”

“…Documenting an elevated serum TSH level confirms the diagnosis of primary hypothyroidism. 49 The presence of TAbs is a useful confirmatory finding. Serum TSH >2.5 mU=L in pregnant women should be used as a guide for thyroid dysfunction.…”

Iodine Status in Pregnant Women in the National Children's Study and in U.S. Women (15–44 Years), National Health and Nutrition Examination Survey 2005–2010

“…To support fetal and infant thyroid function, the Institute of Medicine suggests an RDA for pregnant women of 220 lg iodine per day and 290 lg iodine per day during breastfeeding (10). To prevent iodine deficiency, the American Thyroid Association recommends supplementation containing 150 lg of iodine daily for U.S. women of childbearing age during the preconception phase, as well as during pregnancy and lactation (11). In addition, adequate iodine intake before conception (RDA of 150 lg per day) is important to ensure adequate maternal iodine stores to support the fetus.…”