Iodine, as the main raw material for the synthesis of thyroid hormones in the body, exhibits a U-shaped curve relationship with thyroid function. Both iodine deficiency and excess may cause thyroid dysfunction and damage human health. China was once one of the countries where iodine deficiency were widely prevalent in the world. Since the implementation of universal salt iodization in 1995, the iodine nutritional status in China has been greatly improved, and the goal of eliminating iodine deficiency disorders has been basically achieved. However, there is still a state of inadequate iodine nutrition among susceptible populations (pregnant women, breastfeeding mothers and infants). Pregnancy is a special physiological stage for women, and in order to meet the iodine needs of themselves and their fetuses, the iodine requirement of pregnant women increases by about 50% compared to non-pregnant women. WHO/UNICEF/ICCIDD suggest using urinary iodine concentration (UIC) to evaluate iodine nutritional status during pregnancy, with UIC of 150 - < 250 μg/L is considered suitable for iodine nutrition, but the best method for evaluating iodine nutrition status during pregnancy is still controversial. With the improvement of socio-economic level and people's health awareness, especially during special stages such as pregnancy, people pay more attention to individual iodine status. Therefore, the investigation of reliable indicators for evaluating iodine nutrition during pregnancy has gained increasing significance.

Urinary iodine; Pregnancy; Evaluating indicator; Iodine nutritional status