The immune system is the umbrella of our body that identifies external enemies, fights against them and protects our health. The immune system consists mainly of immune organs and immune cells. A part of the immune cells acts as a patrolman, patrolling and monitoring with the blood in the body, searching for the presence of invading foreign enemies (including microorganisms such as bacteria and viruses, as well as exogenous tissues that do not belong to them). When they find an invading foreign enemy, the body will sound the alarm and enter a state of readiness. First, it will mobilize more “patrol” to join the emergency treatment, they can directly attack the enemy, but also can secrete antibodies, indirectly fight with the enemy, if at this time still can not eliminate the foreign enemy, they will call another part of the lymphocytes stationed in the lymphatic organs, we collectively fight together against the foreign enemy. In the process of fighting foreign enemies, sacrifices are inevitable, and the lymphocytes produced in the bone marrow are transferred to the lymphatic organs for collective training and transformation, so that the “new recruits” also have the ability to fight foreign enemies. And what is the role of the immune system in pregnancy? We know that half of the fetus’ genes come from the mother and the other half from the father, so our body defaults to exogenous tissues, but the mother is great at opening an umbrella of protection for the fetus from her own immune system against her own fetus. However, when the immune system is hyperactive, the umbrella is weakened and immune cells and antibodies attack the fetus in the mother’s body, resulting in clinical infertility or miscarriage. For patients undergoing assisted reproduction, immune screening is recommended in the following cases: 1. Primary infertility For patients who have never had a pregnancy, we recommend immune screening, especially if the cause is unknown. If there are no obvious abnormalities in both male and female tests, we must consider whether the female partner has a hyperfunctional immune system that repeatedly resists the attack, resulting in the embryo’s non-fertilization. However, we inevitably wonder whether immune screening is still necessary if there is obstruction of the fallopian tubes in the female partner or severe oligozoospermia in the male partner causing infertility. In fact, the answer is yes, because at this time we cannot assess the time of tubal obstruction or the time of semen quality decline, the fallopian tubes may be open and the semen may be normal when you first start to try to conceive, therefore, immune screening is needed before entering the fertility treatment to exclude the immune abnormalities that cause infertility. 2. History of spontaneous abortion Spontaneous abortion mainly refers to spontaneous fetal expulsion and embryonic abortion caused by non-human factors, and in a broader sense, biochemical pregnancy is also included. If you have had one or more previous spontaneous abortions, it is recommended that you undergo immune screening to rule out miscarriage due to a hyperactive immune system attacking the embryo. 3. Repeated implantation failure For patients with primary infertility, there is no doubt that immune screening is indicated after several unsuccessful embryo transfers. However, for patients who have had normal children in the past or who have had abortions or medication abortions due to personal factors, should they also undergo immune screening? In fact, it is also necessary because the immune system is constantly adjusting to what we are exposed to or to microorganisms such as viruses, etc. There are many cases of immune infertility or immune miscarriage after normal childbirth. Therefore, immune screening is recommended whenever you have multiple transfers of quality embryos without pregnancy. In conclusion, the immune system is our good friend and it provides us with an umbrella of protection against external enemies and protects our health, but excessive immune protection may play a negative role in pregnancy. It is recommended that you undergo immune screening at the right time during assisted reproduction, and hopefully when you push the door of immune screening, you will be greeted with a successful pregnancy.