The placenta generally has the roles of material exchange, defense, synthesis and storage of nutrients. 1. Material exchange: oxygen and carbon dioxide can be exchanged within the placenta; it can supply nutrients to the fetus and expel metabolic products from the fetus. 2. Defense: the placenta has a certain defense function, some bacteria, toxoplasmosis, chlamydia, etc. can not pass through the placental barrier. 3. Synthesis: The placenta can synthesize some hormones, such as human chorionic gonadotropin, estrogen, progesterone, cytokines and growth factors. 4. Storage of nutrients: Some nutrients such as proteins, glycogen, calcium, iron, etc. can be stored in the placental cells to meet the growth and development needs of the fetus. The placenta is an important organ for the exchange of materials between the fetus and the mother. Regular checkups should be conducted during pregnancy to avoid abnormalities such as implantation of the placenta. During pregnancy, you should pay attention to rest, relax and avoid tension and anxiety. If you have any discomfort, you should go to the hospital in time to get a clear diagnosis from the doctor and cooperate with the doctor to deal with the symptoms.