Background: Pregnancy loss (PL), the most common negative outcome of pregnancy, has an important emotional impact on women and their partners. Aim of the work: This work aims to assess serum vitamin D status among pregnant females with and without abortion and to determine possible risk factors influencing vitamin D deficiency among pregnant females. Participants and Methods: a case control study included250 pregnant women during the first 20 weeks of gestation, aged from 20 to 35 years. Cases comprised those presented with current idiopathic abortion (125), while those without current or previous abortion were selected as controls chosen from attendees of Obstetric and Gynecological Department of Al Zahraa University Hospital in Cairo, Egypt during 2017&2018. The data were collected by completing interview questionnaire, taking anthropometric measurement (weight and height) then calculating body mass index (BMI) and taking blood sampling to assess vitamin D level. Results:Vitamin D deficiency (VDD) and insufficiency were high among all studied pregnant women (deficient in 57.5% and 60%, insufficient in 32.5% and 27.5% of cases and controls respectively) while optimal level was only among 10% of cases and 12.5% of controls with OR =1.28 and C.I = (0.319- 5.186) . By comparing deficient and optimal groups, it was found that obesity (OR=1.5), nullipara parity (OR=7.77), less indoor activity (OR=1.4) and less outdoor activity (OR=16.47), more fish intake (OR=19) and less yogurt consumption (OR=1.57) were possible risk factors for VDD, while urban residence, no working status, low educational level; low socio economic status, white skin color and exposure to sun with more duration and more body surface exposed were protective factors. Conclusion:Vitamin D deficiency was more among pregnant females and it was detected as one of the possible modifiable risk factors of spontaneous pregnancy loss especially among recurrent ones.