Iodine is an essential micronutrient for the synthesis of thyroid hormones and for growth and development in the human body. Recent studies have revealed that iodine can exert biological functions beyond the thyroid. By modulating oxidative stress and gut microbiota abundance, it influences systemic metabolic homeostasis. Imbalance in iodine nutrition during pregnancy is closely associated with the onset and progression of gestational metabolic diseases. Based on studies pertaining to the relationship between iodine nutrition during pregnancy and gestational metabolic diseases from 1980 to 2025, this review summarized the relationship of iodine nutrition during pregnancy with gestational metabolic diseases, including gestational diabetes mellitus, gestational hypertension and preeclampsia, gestational overweight or obesity, and gestational dyslipidemia, and described the underlying biological mechanisms, so as to provide the evidence for formulating prevention and control strategies for gestational metabolic diseases.