Background: Iodine nutrition during pregnancy has become an important public health concern because of the deleterious impact of iodine deficiency on brain development during fetal and early postnatal life. Iodine nutrition status can be assessed in a population by the median urinary iodine concentration (UIC). World Health Organization, the United Nations Children's Fund, and the International Council for Iodine Deficiency Disorders have established that a median of UIC between 150 and 249?µg/L in pregnant women indicates an adequate iodine intake. The aim of this study was to assess iodine nutrition status in Mexican pregnant women.

Methods: Two hundred ninety-four pregnant women receiving prenatal care in the Public Medical Units of the State Ministry of Health for each pregnancy trimester (first, n=60; second, n=103; and third, n=131) in Queretaro, Mexico, were enrolled to assess UIC by the Sandell-Kholtoff method.

Results: The median of UIC was 273, 285, and 231?µg/L in the first, second, and third trimesters of gestation, respectively. Globally, the median (range) of UIC was 260 (5–1320) µg/L, and the percentage of samples with UIC below 150?µg/L was 28%. There was no significant difference between the UIC of women using iodine-containing multivitamins compared with those who reported the consumption of noniodized multivitamins (p>0.05). In addition, we found no difference between the UIC of women using iodized table salt compared with those who employed noniodized table salt, with those who did not know whether their table salt was iodized (p>0.05).

Conclusions: Based on the median UIC, iodine intake in Queretaro, Mexico, is slightly above requirements during the first two trimesters, and adequate in the third trimester. The wide Mexican universal iodized salt program seems to supply adequate dietary iodine to pregnant women without health insurance in this region. However, regular monitoring of iodine status is recommended during pregnancy throughout Mexico.