Materials and Methods: In a retrospective cross-sectional study, all pregnant women with any gestational age without receiving vitamin D supplement before 3 months of pregnancy from two private offices of gynecologists in Rasht were studied from spring 2013 till summer 2014. All data were collected, recorded and blood sampling was done to measure serum 25 (OH) vitamins D. Vitamin D deficiency and insufficiency was defined as levels of 25 (OH) D < 20 and < 30 ng/mL for pregnant women, respectively. All data were analyzed by descriptive and analysis tests.

Results: The mean age of pregnant women was 27.5 ± 4.6. Mean serum 25(OH) D of pregnant women was 15.6 ± 9.8 mg/dL; vitamin D deficiency and insufficiency was observed in 69.3% (124 subjects) and 20.7% (37 subjects) of cases, respectively. Also, there was a positive correlation between the vitamin D levels and vitamin D consumption as a supplementary one before pregnancy (r = 2.473, P = 0.001)

Conclusion: Vitamin D deficiency in pregnant women is higher in this area (Guilan province). Vitamin D supplementation can help to increase 25(OH) D levels. However, women should ideally start vitamin D supplementation a few months before getting pregnant.