Folic acid is a vitamin with a single active ingredient that can prevent fetal malformations, so from the first 3 months of pregnancy until the end of the second 3 months, it is necessary to take 0.4 to 1 mg of supplementation per day, and it is recommended that women who are preparing for pregnancy take it regularly. The first 3 months of pregnancy is an important period for the development of the neural tube of the fetus, so pregnant mothers should continue to take oral folic acid supplements to prevent the appearance of neural tube malformation of the fetus. 2, missed folic acid does not need to make up for the folic acid in the human body retention time is relatively short, a day after the body level will be reduced, so folic acid supplements pregnant mothers must take every day, can not miss to take. However, if you miss a dose, there is no need to take it. 3, eat some folic acid-rich food pregnant mothers to supplement folic acid in addition to taking folic acid supplements, but also through the consumption of folic acid-rich food supplement folic acid. 4, you should start taking folic acid before pregnancy neural tube deformity is the most serious congenital malformation that endangers human health, manifested as anencephaly and spina bifida, etc.. China is a country with a high incidence of neural tube malformation. 5, whether the more folic acid supplementation is the better too much folic acid supplementation will not only affect the absorption of zinc in the human body, affecting the intellectual development of the fetus, but also mask the early symptoms of vitamin B12 deficiency, leading to neurological damage and affecting the hematopoietic function of the body. In addition, excess folic acid in the body can interfere with the action of anticonvulsant drugs. Special attention should be paid to the following three categories of women who are preparing for pregnancy and need to focus on folic acid supplementation: 1. Women with multiple spontaneous miscarriages and embryonic abortions should also pay attention to reasonable folic acid supplementation. Ideally, serum folate levels, intraerythrocyte folate levels and homocysteine testing and genetic testing for folic acid metabolism disorders should be performed, and if there are low folate levels or genetic mutations for folic acid metabolism disorders, they need to be under the guidance of a doctor Scientific high-dose folic acid supplementation with regular follow-up. The probability of reoccurrence is 2%-5% for women who have had one child with neurological defects and 30% for those who have had two children with the same defects. 3. Women in mountainous or highland areas who often do not eat green leafy vegetables and citrus. How long does it take to get out of the danger period? First of all, our obstetrics department takes 28 weeks as the boundary. Before 28 weeks, the placenta is in a low position, close to, adjacent to or covering the endocervix, which is called “placenta hypotrophy”. At this time, if the vaginal bleeding is not very serious and endangering the life of mother and child or premature rupture of membranes, we will continue to observe the placenta, as the uterus grows, the edge of the placenta may move up, but how long is not guaranteed, only regular ultrasound to understand the status of the placenta. After 28 weeks, it is called “placenta praevia”, until delivery, the placenta has a chance to “grow up”, all you have to do is not to be overly anxious, and not to take it lightly, regular maternity checkups, review ultrasound on time, if there is vaginal bleeding, abdominal pain, fetal movement and other discomforts, seek emergency medical treatment. If you have vaginal bleeding, abdominal pain, fetal movement and other discomforts, you should seek emergency medical treatment in time, and finally deliver the baby in the right way at the right pregnancy week according to the condition of the placenta.