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Immune tolerance in pregnancy or maternal immune tolerance is the immune tolerance shown towards the fetus and placenta during pregnancy. This tolerance counters the immune response that would normally result in the rejection of something foreign in the body, as can happen in cases of spontaneous abortion .
A normal pregnancy contains higher numbers of immune cells, however, in a normal pregnancy, the immune system does not attack the fetus, but works to protect it as it grows and divides at an incredibly fast rate. T helper cells, Th1 and Th2, differ based on cytokine levels; Th1 is up-regulated during pregnancy,whereas Th2 is up-regulated in cancer.
Hemolytic disease of the fetus and newborn is similar to a transfusion reaction in that the mother's antibodies cannot tolerate the fetus's antigens, which happens when the immune tolerance of pregnancy is impaired. In many instances the maternal immune system attacks the fetal blood cells, resulting in fetal anemia.
Microchimerism is a result of pregnancy, possibility that foreign cells were of transfusion or transplantation origin was rejected due to women's health. Women testing positive for male origin microchimerism cells had reduced hazard rates of ovarian cancer than women testing negative. [52] Pregnancy at older ages can reduce risk of ovarian cancer.
A better understanding of the immunology of pregnancy may lead to the discovery of reasons for miscarriage. [citation needed] Regulatory T cells (Tregs) appear to be important in the maintenance of tolerance to fetal antigen. Increased numbers of Tregs are found during normal pregnancy.
Exposure to fetal blood cells that can cause RhD alloimmunization can happen during normal pregnancy and delivery, miscarriage, amniocentesis, cordocentesis, chorionic villus sampling, external cephalic version, or trauma. [3] [8] 92% of women who develop an anti-D during pregnancy do so at or after 28 weeks gestation. [11] [9] [12]
Unlike hemolytic disease of the fetus and newborn, NAIT occurs during the first pregnancy in up to 50% of cases, [1] and the affected fetuses may develop severe thrombocytopenia (<50,000 μL −1) very early during pregnancy (as early as 20 weeks gestation, consistent with the development of platelet antigens, [1] and the majority of the time ...
Cell-free DNA can be used the determine the Rh antigen of the fetus when the mother is Rh negative. Blood is taken from the mother during the pregnancy, and using PCR, can detect the K, C, c, D, and E alleles of fetal DNA. This blood test is non-invasive to the fetus and is an easy way of checking antigen status and risk of HDN.