Introduction: Biosynthesis of thyroid hormone and consequently the requirement for iodine have been established to increase during gestation mainly due to increased iodine demand by the fetus. Therefore, diminished iodine intake by the mother during early pregnancy eventually leads to the development of iodine deficiency disorders(IDDS)  in the offspring. The present study aimed to explore the pattern of urinary iodine excretion during gestation in urban districts of Urmia County.

Methods: In this cross-sectional study, 40 women at 1^st trimester were enrolled. Exclusion criteria consisted of history of miscarriage and thyroid malfunction. Random urine samples were collected at 1^st -, 2^nd – and 3^rd trimesters. In fact, UIC was determined via the sandell-kolthoff-method.

Results: Median UIC at 1^st- , 2^nd- and 3^rd trimester were reported 116.5 µg/L, 98.8 µg/L and 100   µg/L, respectively. Repeated measurement revealed no Significant differences in median UIC during gestation (P=0.2). Prevalence of iodine deficiency (UIC<150 µg/L) at 1^st -, 2^nd – and 3^rd trimesters were 72%, 75% and 86%, respectively.

Conclusions: The findings of the present study revealed that median UIC (105.1 µg/L) among pregnant residents of Urmia County was lower than the values recommended by WHO for school-age children and non-pregnant women. Accordingly, prevalence of iodine deficiency (UIC<150 µg/L) was demonstrated to be substantially higher compared to those regions with adequate Iodine intake. These findings imply that pregnant women residing in urban districts of Urmia are iodine deficient.