I is essential for thyroid hormone synthesis and neurological development. Various changes occur in thyroid hormone metabolism during pregnancy and I requirements increase significantly. The purpose of this study was to investigate I status among pregnant women in Trabzon, formerly a severely I-deficient area but shown to have become I sufficient following mandatory iodisation of table salt based on monitoring studies among school-age children (SAC) in the area. A total of 864 healthy pregnant women with a median age of 28 (25th–75th percentile 17–47) years participated in the study. None of them were using I-containing supplement. All of them were screened for use of iodised salt, obstetric history, thyroid function tests and urinary I concentrations (UIC), and thyroid ultrasonography was performed. Median UIC was 102 (25th–75th percentile=62–143) μg/l. Median UIC of the patients according to trimesters were 122 µg/l at the 1st, 97 µg/l at the 2nd and 87 µg/l at the 3rd trimester. UIC in the 1st trimester was higher compared with the 2nd and 3rd trimesters (P<0·017). Nodules were present in 17·7 % of women (n 153). The rate of iodised salt usage among pregnant women was 90·7 %. Our study demonstrates that, although the I status among SAC has been rectified, I deficiency (ID) is still prevalent among pregnant women. Current knowledge is in favour of I supplementation in this group. Until the effects of maternal I supplementation in mild ID have been clarified by large-scale prospective controlled trials, pregnant women living in borderline defficient and I-sufficient areas, such as Trabzon city, should receive 100–200 µg/d of I-containing supplements in addition to iodised salt.