Iodine deficiency and thyroid function in healthy pregnant women

BACKGROUND AND OBJECTIVE: Studies from Spain suggest that the intake of iodine in pregnant women is below nutritional requirements. This study was designed to determine iodine intake and its relation with thyroid volume during pregnancy in women from southeast Spain. PATIENTS AND METHOD: A total of 520 healthy pregnant women were studied during the full three trimesters of their pregnancy. A control group was composed of 373 non-pregnant women. The following variables were measured: TSH, FT3, FT4, thyroglobulin, antiperoxidase antibodies, urinary iodine levels, and thyroid volume. RESULTS: Median urinary iodine levels were below 100 mug/l in the controls and the pregnant women during their first trimester. These levels rose progressively and significantly over the second and third trimesters. Thyroid volume increased during the second and third trimesters compared with the first. TSH levels were lower during the first trimester compared to controls, and increased significantly during the third trimester. FT4 levels fell significantly during the third trimester. There was a significant negative correlation between TSH levels and thyroid volume (r = -0.22; p = 0.005). CONCLUSIONS: Iodine intake in pregnant women in Malaga is low. The results suggest a deficit in thyroid function secondary to iodine deficiency, which is worsened as pregnancy advances. The data support the convenience of systematic administration of an iodine supplement in healthy pregnant women.