Variation of Urinary Iodine Concentration Within a Month During the First Trimester of Pregnancy in Tehran an Iodine-Repleted Area and Comparison to Non-Pregnant Women

In order to assess variations of urinary iodine concentration (UIC) during a 4-week period among pregnant and non-pregnant women in an iodine-replete area. Pregnant and non-pregnant women referred to two maternity hospitals in Tehran were consecutively recruited from September 2005 to March 2006 urine samples (5–10 mL) were collected on an every-other-day basis for 4 weeks (i.e., 12 samples for each individual). UIC was determined using modified Sandell-Kolthoff method. Thirty-six pregnant and 32 non-pregnant women completed the study. Mean±SD age of pregnant women was 27.4±6.4 and that of non-pregnant women was 27.6±4.5 years (p=0.897). Mean±SD gestational age was 11.0±3.3 weeks in pregnant participants. Median UIC of <100, 100-149, 150-249, and ≥250 µg/L was present in 19.4, 25.0, 30.6, and 25.0% of pregnant, 15.6, 37.5, 34.4, and 12.5% of non-pregnant, and 17.6, 30.9, 32.4, and 19.1% of total individuals, respectively. Median UIC values of sample, numbers 1 to 12 were not significantly different either in pregnant (p=0.591) or in non-pregnant subjects (p=0.745), except for sample number 11, median UIC was not significantly different between pregnant versus non-pregnant women (P values > 0.05). Mean SD value for UIC in samples number 1 to 12 in pregnant women was 138.4 (24.1–404), whereas in non-pregnant women this value was118.0 (29.5-272.4) µg/L (p=0.286). There was a wide intrapersonal variation in UIC values among pregnant and non-pregnant women residing in an iodine-replete area, supporting the notion that casual UIC would not reflect iodine status of the individual.