Abstract: Objective: To explore the relationship between the deficiency of folic acid during gestational period and gravida megaloblastic anemia and fetus neural tube defect. Methods: One thousand and forty-one gravidas from out-patients clinic for regular prenatal care were investigated,whose first identification were from 12 to 14 weeks of pregnancy. All gravidas were divided into two groups( A and B group) according to oral folic acid administrate or not 3 months befor and after pregnancy. Group A( 614 cases) took folic acid by oral from 3 months( at least 1 month) before pregnancy to 3 months after pregnancy. Group B( 427 cases) did not take folic acid by oral. Blood analysis,the serum content of folic acid and B ultrasound of two groups were investigated to compare the occurrence of gravida megaloblastic anemia and fetus neural tube defect. Results: The levels of red cells and serum folic acid of group A were significantly higher than that in group B( P 0. 01). The incidence of megaloblastic anemia of gravida taking folic acid by oral in 3 months( at least 1 month) before pregnancy was obviously lower than that in B group( P 0. 01). Compared with B group,the incidence of fetus neural tube defect of A group was decreased. Conclusions: Gravida who takes folic acid by oral 3 months befor and after pregnancy can reduce the incidence of gravida megaloblastic anemia and fetus neural tube defect.