Background: pregnant women in resource-poor areas are at risk of multiple micronutrient deficiencies, and diets that are low in animal products place women at increased risk of vitamin B12 deficiency. Aim of the Work: to investigate the vitamin B12 status of pregnant women in Egypt and its relationship with obesity and gestational diabetes mellitus (GDM). Patients and Methods: this clinical observational prospective study has been conducted at Bab Al-Shaaria University Hospital Obstetrics and Gynecological Department from April 2018 to January 2019. To assess vitamin B12 status among pregnant woman and its association with obesity and gestational diabetes. 80 pregnant women attended to out-patient clinic were included in the study. The evaluation included data collection through: history taking, examination, anthropometric measurement, maternal blood vitamin B12 level estimation at second and third trimester and blood glucose level. Results: vitamin B12 deficiency in pregnancy is common particularly in obese women and those with GDM. Conclusion: vitamin B12 deficiency is silent and common in general population. Causes of vitamin B12 deficiencies are multifactorial and associated with many health problems. Also, obesity is common and its prevalence is increasing in the world. Therefore, both health problems have gained importance in family medicine practice in the last decades.