Iodine Supplement Strategies Between Routine Iodine Supplementation and Selective Iodine Supplementation

Inclusion Criteria: * first visit for antenatal care in the first trimester * singleton pregnancy * delivered at Maharaj Nakorn Chiangmai Hospital Exclusion Criteria: * thyroid disease which diagnosed before pregnancy or currently * history of thyroid gland surgery or iodine ablation therapy * received iodine supplement before pregnancy * received any medication for thyroid disease treatment, within 6 weeks postpartum women or breast feeding period * family history of thyroid disease * having underlying disease or contraindication which cannot received iodine supplement * loss follow-up or incomplete data.