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Due to the increasing nutritional requirements in the pregnancy, taking certain micronutrients as dietary supplements and thus minimizing the risks associated with deficiency is of great importance in the protection of maternal and fetal health. In pregnancy, dietary supplements are vital in severe or moderate deficiency of nutrients, also bring various risks in conditions of mild deficiency or adequate maternal nutrient storage.The effect of folic acid supplementation on prevent congenital anomalies, has been proven. In maternal period, excessive intake of folic acid may cause carcinogenicity, negatively affect the absorption of zinc, lead to delays in the diagnosis and treatment of vitamin B12 deficiency, and may be associated with the risk of childhood asthma and allergy. Vitamin B12 is another vitamin whose deficiency is associated with fetal anomalies. Although the toxic effect of vitamin B12 is not reported, a case report showing allergic reactions was found in the literature review in case of excessive intake. Vitamin D, which is beneficial in the prevention of neonatal hypocalcemia and rickets, excessive intake of the supplement may be a teratogenic effect. Iodine supplement is effective in preventing diseases such as cretinism associated with iodine insufficiency. However, it has been stated that excessive intake of iodine supplement may lead to an increase in the prevalence of thyroid dysfunction of the pregnant woman, subclinical and overt hypothyroidism during pregnancy and negatively affect the psychomotor development of the baby. The use of nutritional supplements at the recommended doses during pregnancy is appropriate, but attention should also be paid to excessive intake as well as prevention of insufficiency. In this review, the risks of excessive intake of folic acid, vitamin B12, vitamin D, and iodine supplements used in pregnancy are discussed.