Iodine intake in pregnancy

Iodine is an essential micronutrient required for thyroid hormone biosynthesis. The recommended daily adult intake is 150 μg, increasing to 220–300 μg for pregnant and lactating women. Urinary iodine concentration (UIC) is an accurate indicator of iodine intake because more than 90% is excreted over a 24-hour period. The World Health Organization, United Nations Children’s Fund, and the International Council for the Control of Iodine Deficiency Disorders established that for a given population, the appropriate UIC in clinically healthy pregnant women should be 150–249 μg/L [1] and [2]. Iodine deficiency disorders (IDDs) are implicated in several diseases [3]. Despite iodine prophylaxis programs in many countries, iodine deficiency is still a significant public health concern [4]. Following the introduction of a salt iodization program (30 mg/Kg of salt) in Italy in 2005, we wanted to investigate whether the increased iodine requirement during pregnancy is being met in an urban area of Rome. Between January 2007 and March 2008, 124 clinically healthy pregnant women were enrolled to evaluate UIC in spot urine samples collected in the morning. The mean age of the women was 32 years, and mean body mass index (BMI, calculated as weight in kilograms divided by height in meters squared) was 25.3 ± 2.6. Fifty-seven women were in the first trimester of pregnancy, 34 in the second, and 33 in the third. A control group of 145 age-matched healthy nonpregnant women (mean age 30 years; mean BMI 24.2 ± 2.4) was also enrolled. All participants were resident in the urban area of Rome and had no restrictions on iodized salt intake. Informed consent was obtained from each participant. The mean UIC in the control group was 137.2 ± 5.9 μg/L (median 112 μg/L, range 62–465), but it was significantly lower in the pregnant women (P < 0.01). Mean UIC in the women who were in the first, second, and third trimesters of pregnancy were 93.6 ± 6.6 μg/L (median 85 μg/L, range 28–223), 90.11 ± 6.4 μg/L (median 82 μg/L, range 25–165), and 89.8 ± 3.6 μg/L (median 88 μg/L, range 39–113), respectively (Fig. 1). Notably, severe iodine deficiency (UIC less than 50 μg/L) was found in 12 pregnant women who were in the first trimester, 2 in the second, and 2 in the third. These results demonstrate that even in an urban area where iodine intake is expected to be adequate, pregnant women may be at risk of IDD. They also indicate the need to monitor iodine intake during pregnancy in areas with recently established salt iodization programs, and raise the question of whether iodine supplementation in pregnancy should be generalized or tailored on an individual basis.