Closed antibodies are mainly found in pregnant women’s bodies, and their main function is to protect the embryo, preventing the woman’s immune system from mistaking it for a foreign body from the outside world, preventing the pregnant woman’s immune system from attacking or devouring the embryo, and serving to protect the fetus from normal implantation and development. A normal pregnant woman should have a positive reaction for closed antibodies. If the closed antibody is negative it will cause the mother’s immune system to attack the embryo or fetus, causing immune infertility. Most pregnancies result in spontaneous abortion. Once a pregnant woman is diagnosed with negative closed antibodies, she needs to be kept pregnant. Immunotherapy can be used to make the closed antibodies positive and the fetus can develop normally.