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

Background: This report presents iodine data from National Health and Nutrition Examination Survey (NHANES) and from a sample of pregnant women in the National Children's Study (NCS) Vanguard Study. Methods: Urinary iodine (UI) was measured in a one third subsample of NHANES 2005-2006 and 2009-2010 participants and in all 2007-2008 participants age 6 years and older. These measurements are representative of the general U.S. population. UI was also measured in a convenience sample of 501 pregnant women enrolled in the NCS initial Vanguard Study from seven study sites across the United States. Results: NHANES median UI concentration in 2009-2010 (144 mu g/L) was significantly lower than in 2007-2008 (164 mu g/L). Non-Hispanic blacks had the lowest UI concentrations (131 mu g/L) compared with non-Hispanic whites or Hispanics (147 and 148 mu g/L, respectively). The median for all pregnant women in NHANES 2005-2010 was less than adequate (129 mu g/L), while third trimester women had UI concentrations that were adequate (median UI 172 mu g/L). Third trimester women participating in the NCS similarly had an adequate level of iodine intake, with a median UI concentration of 167 mu g/L. Furthermore, NCS median UI concentrations varied by geographic location. Conclusions: Dairy, but not salt, seafood, or grain consumption, was significantly positively associated with median UI concentration in women of childbearing age. Pregnant women in their third trimester in the NHANES 2005-2010 had adequate median UI concentrations, but pregnant women in NHANES who were in their first or second trimesters had median UI concentrations that were less than adequate. Non-Hispanic black pregnant women from both the NHANES 2005-20010 and the NCS consistently had lower UI median concentrations than non-Hispanic whites or Hispanics.