Vitamin B12 deficiency is associated with obesity and overweight, anemia and possible uterus and fetus neurological impairments. This study was aimed to reveal a health risk for pregnant women with vitamin B12 deficiency, as well as the preterm birth one. The findings demonstrated no strong correlation between serum vitamin B12 level and preterm birth risk. But an inverse association between vitamin B12 level and overweight before pregnancy as well as when giving birth was found. There was confirmed the noteworthy connection between meat consumption and vitamin B12 level, as well a correlation between the vitamin B12 level and that of hemoglobin in pregnant women was found. The need in further investigation was emphasized to increase the reproducibility of results.