Objective  To examine iodine nutrition status among pregnant women in Ji'nan city, Shandong province for providing evidence to effective improvement of iodine nutrition in pregnant women.

  Methods  A monitoring survey was conducted among 4 992 pregnant women recruited in 12 districts/counties of Ji′nan municipality, Shandong province during 2018 – 2021; each of the districts/counties was divided into 5 geographical regions and 20 pregnant women were selected from one subdistrict/town in each of the 5 regions. Table salt samples were collected from households of the pregnant women and urine samples of the pregnant women were also collected. Iodine content of table salt samples was measured with direct titration listed in the General Test Method for Salt Industry: Determination of Iodine (GB/T13025.7) and that of well salt and other fortified table salt samples was determined with arbitration method. Urinary iodine was detected using arsenic cerium catalytic spectrophotometry stated in WS/T107 issued by National Health and Family Planning Commission. Year- and trimester-specific urinary iodine were analyzed.

  Results  The median ( 25% percentile P₂₅, 75% percentile P₇₅) of iodine content was 22.31 (18.18, 25.59) mg/kg for all the 4 992 table salt samples. The coverage rate of iodized table salt was 88.92% (4 439 samples) and the usage rate of qualified iodized table salt was 72.96% (3 642 samples). There were significant yearly and regional differences in iodized salt coverage (χ² = 72.54, χ² = 271.04; both P < 0.05) and qualified iodized table salt usage rate (χ² = 43.03, χ² = 492.25, both P < 0.05); but the iodized salt coverage and qualified iodized table salt usage rate were not significantly different among the pregnant women in various trimesters of pregnancy (χ² = 1.07, χ² = 0.97; both P > 0.05). The median ( P₂₅, P₇₅) of urinary iodine was 145.70 (87.70, 216.00) μg/L for the 4 992 pregnant women. The urinary iodine concentration differed significantly among the pregnant women surveyed in different years (H = 21.97), from various districts/towns (H = 348.78), during various trimesters of pregnancy (H = 41.18), and consuming table salt with different iodine content (H = 13.23) (P < 0.05 for all).

  Conclusion  Mild iodine deficiency existed among pregnant women in Ji'nan city during 2018 − 2021, suggesting that relevant measures should be taken to prevent iodine deficiency in the pregnant women.