Immunology of pregnancy
Alterations in local immune function occur during the course of a woman's menstrual cycle that result in changes in the quantity and distribution of immune cells within the female genital tract. As the uterus prepares for pregnancy and after conception occurs, additional changes in local immunity allow the maternal immune system to recognize but not react against the semi-allograft fetus. Uterine natural killer cells, a specialized immune cell subpopulation that is found within the uterus in increasing amounts during gestation, appear to be imperative for successful placental trophoblast invasion early in pregnancy. Shifts in the patterns of cytokine release by T helper cells during the course of pregnancy appear to produce changing inflammatory responses that aid in the successful continuation of pregnancy. Some changes in the maternal immune system can be seen systemically as well as locally. The frequency of flares and periods of remission of many autoimmune disorders are also affected by gestational changes in local and systemic immune responses. When the necessary immune shifts do not occur, pregnancy pathologies such as preterm labor, preeclampsia, and isolated or recurrent pregnancy loss may occur.
