Recent studies indicate a widespread deficiency of vitamins and minerals among pregnant and lactating women around the world. Most of the women examined (up to 80%), regardless of age, place of residence and professional affiliation, have a combined deficiency of three or more vitamins. Even with the most balanced diet, a diet adequate to the pregnant woman’s energy consumption is not able to provide the growing needs of the body with the necessary amount of minerals and microelements, which contribute to a change in the size and functional activity of the mother’s organs and systems during pregnancy, normal formation of the placenta, and fetal development. Magnesium deficiency leads to a violation of the processes of placentation and the threat of termination of pregnancy in the first trimester. The success of pregnancy largely depends on adequate implantation, the transformation of the spiral arteries and placentation with the establishment of full blood flow in the mother – placenta – fetus system. Violation of the formation of the placenta in early pregnancy leads subsequently to the development of placental dysfunction. Such a “physiological” magnesium deficiency during pregnancy in the absence of adequate nutritional subsidies can increase the risk of early and late miscarriages, premature births due to increased contractile activity of the myometrium, preeclampsia, etc. Chronic magnesium deficiency, which often leads to serious pregnancy complications, must be compensated for by the ingestion of magnesium supplements. Moreover, due to the fact that a mainly long course of treatment is required, in addition to the effectiveness of the action of magnesium-containing drugs, the bioavailability of magnesium and the safety of use are extremely important. Magnox Pregna biomagnesium complex is a unique combination of magnesium and vitamins B1, B6 and E, the use of which helps to suppress contractile activity of smooth and striated muscles (including the uterus), prevent and eliminate leg cramps, reduce the risk of developing hypertension, and the occurrence of eclampsia and premature birth. Key words: magnesium deficiency, vitamins, trace elements, pregnancy, complications, Magnox Pregna biomagnesium complex.