Spontaneous miscarriage and stillbirth Spontaneous miscarriage can be manifested as a dead embryo or fetus that remains in the uterine cavity and has not been expelled, i.e., the embryo stops developing. Since the 1960s, both UU and MH have been associated with spontaneous abortions. Quinn et al. reported a higher rate of UU detection in the lower genital tract in women with a history of three or more miscarriages than in women with normal fertility 83.3%:25.5%. Most of the positive pregnant women had spontaneous regression with the continuation of pregnancy. This may be related to the change in the environment in which mycoplasma lives, as the optimal pH environment for mycoplasma is alkaline (pH 7.6-8.6). The possible mechanisms of spontaneous abortion caused by mycoplasma infection are: mycoplasma infection triggers an inflammatory response in the endometrium, and inflammatory cells, mainly macrophages, infiltrate the endometrium, and macrophages secrete large amounts of tumor necrosis factor alpha (TNF2α) and prostaglandin F2α, which can damage the growing embryo or interfere with the implantation of the embryo. It may also interfere with the regulatory mechanism of the maternal immune system to protect the embryo and cause early miscarriage. Due to the change of endocrine level in pregnant women, the body’s ability to defend itself against pathogens is reduced and latent infection may change to active infection due to pregnancy. Quinn and colleagues reported a controlled antibiotic treatment study of 62 patients with a history of pregnancy miscarriage with positive genital or urinary mycoplasma cultures. This result indicates that subclinical mycoplasma infection is an important cause of spontaneous abortion, especially recurrent abortion. Second, chorioamnionitis, intra-amniotic infection, premature rupture of membranes, preterm delivery, neonatal infection, and postpartum infection Pregnant women infected with UU and MH can cause serious consequences. Several studies have concluded a significant correlation between the isolation of UU from the chorionic amnion and histological chorioamnionitis. Mycoplasma can invade the amnion, leading to clinically significant intra-amniotic infections. Infection of the amniotic cavity can lead to premature rupture of the fetal membranes, preterm delivery, and neonatal infection. The metabolites and secreted enzymes of UU and MH produce direct cytotoxic effects on amniotic membrane and chorionic villus cells, predisposing to premature rupture of the fetal membranes ( PROM); mycoplasma can stimulate immunoreactive cells to produce excessive cytokines, mediating the inflammatory response of the organism causing tissue damage, exudation of inflammatory cells at the site of infection, infiltration of leukocytes, tissue edema, proliferation of fibrous tissue, loss of elasticity or This leads to increased fragility and decreased toughness, which can cause premature rupture of membranes and preterm delivery; pneumonia, enteritis, encephalitis and sepsis in the fetus. For pregnant women, amniotic cavity infection can cause postpartum endometritis, peritonitis and sepsis. Cervicitis can be caused by any cause of cervical mucosal damage and destruction of the barrier structure. Mycoplasma can reside in the vaginal mucosa and live in symbiosis with other flora, developing into a pathogenic microorganism when the immune system is low or the mucosa is damaged. The degradation products of UU can increase the pH of the vagina, facilitating the reproduction and infection of other bacteria. Studies have found that UU combined with infection by other vaginal pathogens can increase the incidence of cervicitis. The possibility of UU infection should be considered in cases of cervical inflammation, prolonged and recurrent disease, and testing for cervical Mycoplasma solium is required. The treatment of UU should be accompanied by attention to the treatment of other vaginal pathogenic bacteria. IV. Pelvic inflammatory diseases Pelvic inflammatory diseases are a group of diseases caused by inflammation of the upper female reproductive tract, including endometritis, tubal inflammation, and tubo-ovarian cysts. Combining experimental results and clinical experience, we deduce that simple UU infection may trigger mild to moderate inflammation of the genital tract, which destroys the local anti-infective effect of IgA on the mucosal surface of the urogenital tract, adheres to the mucosal surface of the genital tract, invades the cervical mucosa causing cervicitis, and spreads upward to endometritis and tubal endometritis, swelling and edema of the fallopian tubes, and large number of leukocytes infiltrate causing adhesion and occlusion of the tubal lumen fluid accumulation. Many pathogenic microorganisms such as Neisseria gonorrhoeae, Chlamydia and Mycoplasma are involved in the pathogenesis of pelvic inflammatory diseases, mostly mixed infections. V. Infertility Mycoplasma genus infection of the reproductive tract is a high incidence of infertility. uU infection causes cervical inflammation resulting in increased secretions, changes the PH value of cervical mucus, which affects the passage of sperm through the cervix and can damage the mucosa of the reproductive tract, exposing immune cells to sperm and producing anti-sperm antibodies leading to infertility. Studies have reported that it can cause inflammatory pelvic diseases, endometritis, tubal inflammation, adhesions of the fallopian tubes, and pelvic connective tissue inflammation thus leading to infertility or ectopic pregnancy. The mechanism of female infertility caused by Mycoplasma may be related to the following factors; adsorption on the surface of sperm and obstruction of sperm movement; production of neuraminidase-like substances that interfere with the union of egg and sperm; co-antigen with sperm and infection stimulates the body to produce antibodies to damage sperm. According to domestic and foreign literature, Mycoplasma solium has a high isolation rate in couples with unexplained infertility. Some studies have reported higher rates of total and single UU positivity for mycoplasma in women than in men, which may be related to the fact that women are more susceptible to mycoplasma infection than men because of the moist and suitable temperature of the vagina. Therefore, it is of great interest to perform Mycoplasma solium screening in infertile couples.