For pregnant women, it is important to urinate and empty the bladder before the amniocentesis. The pain level of puncture is similar to the usual pain of intramuscular injection, the more tense the abdominal muscles are, the more painful it will be. The doctor will do a good job of positioning before the puncture, and it will generally not cause harm to the fetus. The dressing on the puncture site can be taken off the next day. If you have stomach pain, vaginal bleeding, vaginal fluid or fever, you should go to the emergency room in time. There are also some special groups of people, such as pregnant women with twin fetuses, who need to undergo separate punctures of the two fetuses, and doctors will use special methods to differentiate the amniotic fluid of the two fetuses; there are also pregnant women with special blood type Rh-negative blood group, and the puncture procedure has the risk of increasing the blood exchange between the fetus and the mother and increasing the risk of hemolysis in the newborn, so they need to inject Rh immunoglobulin for active immunization; similarly conditions are patients with active hepatitis B. Amniocentesis may increase the risk of vertical transmission of the hepatitis B virus to the fetus and also requires hepatitis B immunoglobulin. In addition, if there is a fever or abnormally high white blood cells before the puncture, the doctor will suspend or postpone the procedure to confirm that there is no infection before performing the puncture.