Genital tract malformations are not very rare, and according to domestic articles the prevalence is about 0.13% to 0.98%. The actual prevalence is higher than this, as some women do not go to the hospital for examination because they have no obvious symptoms. Reproductive system anomalies include ovaries, fallopian tubes, uterus, vagina and external genitalia. This article discusses the particular problem of combined pregnancies with anomalies of the reproductive tract, thus focusing on the latter three sites. As early as 6-7 weeks of embryonic life, the mesonephric ducts and the common mesonephric ducts, which are the beginning of the genital tract, appear. At 10 weeks, the mesonephric ducts completely degenerate and the lower part of the common mesonephric ducts forms the common mesonephric nodules, which form the urethro-vaginal diaphragm that separates the urethra from the vagina. The unfused cephalic ends of the two middle renal ducts will soon develop into the two fallopian tubes, the fused portion will develop into the uterus and vagina, and the urogenital sinus will form the lower vaginal segment. These differentiation processes are completed by the time the fetus is nearly 5 months old, and the external genitalia develop slightly earlier, with the first female vulva at 3 months of age. During this differentiation process, certain factors such as drugs, viral infections or intrinsic chromosomal abnormalities can hinder the differentiation process, resulting in stalled development or abnormalities. In this case, the terminal development of the middle renal duct is arrested, resulting in partial atresia of the lower part of the vagina, while the upper part develops normally. The uterus is more closely related to the pregnancy, in which one side of the uterus develops unilaterally and the fallopian tube unilaterally due to the disproportionate development of the two middle renal ducts. The other side of the tubule may be obstructed to varying degrees, and may present as either an acinar uterus or a vestigial uterus, with approximately 65% of unicornuate uteruses being combined with a vestigial uterus. It is also possible to form a single-horned uterus and separate fallopian tubes on each side, each with its own function, due to the complete lack of fusion of the two middle renal ducts, i.e., a double uterus and a double cervix, often accompanied by a double vagina. If the fusion of the middle renal canal is obstructed on both sides, it may vary depending on the degree of fusion, and only partial fusion may result in a bicornuate uterus of varying degrees. It can also be completely fused, with a normal uterine shape and a septum that has not disappeared to form a longitudinal uterus of varying degrees. Rarely, uterine malformations also present as two separate uteri with a small channel between the cervix, which is more often located at the level of the isthmus. If the vagina on the longitudinal side is partially atretic, menstrual blood can flow from the opposite vagina through a small channel in the isthmus, a complex malformation that is very rare. The effects of different types of genital tract anomalies on pregnancy and their management: I. Double uterus Double uterus can be two completely separated uterine bodies and cervix, or they can be connected at the cervical part. 1. Complications during pregnancy and delivery The chance of pregnancy with a double uterus is not affected, but the rate of miscarriage and preterm delivery is higher, which may be related to insufficient blood supply to the uterus and poor metaphase formation. The outcome is better if the pregnancy can be continued. Abnormal fetal position, such as breech position, has been reported to occur more than three times as often as in normal women. There is also a high incidence of premature rupture of membranes associated with it. The incidence of intrauterine growth retardation is about 10 times higher than normal due to inadequate blood supply to the uteroplacenta. Hyperemesis and consequent early placental abruption and meconium dystrophy and the occurrence of placenta praevia are common. In addition, acute torsion of the pregnant uterus should be considered in cases of sudden onset of acute abdominal pain, vaginal bleeding, and shock in the middle and late stages of pregnancy, because the uterus is fixed by the broad and round ligaments on only one side of the uterus, and the weight of the uterus is uneven. The occurrence of these symptoms in late pregnancy should also consider spontaneous rupture due to uterine muscle dysplasia. Although these complications are rare, the consequences are extremely serious. One case was reported by Xu Jiaying et al. as a full-term pregnancy, diagnosed by ultrasound at 37 weeks of gestation, with a single vagina and a double cervix, and two fetuses, one at each end and one at the buttocks, which were delivered by cesarean section. The twin uteruses can be delivered by cesarean section due to abnormal fetal position, obstruction of the birth canal by an infertile uterus embedded at the pelvic inlet, weak uterine contractions, and intrauterine hypoxia of the fetus. Postoperative bleeding can also be high due to poor uterine regeneration, and the non-pregnant uterus can discharge the meconium tube type, which can also cause infection due to poor drainage. The diagnosis of double uterus is often confirmed by the discovery of longitudinal vaginal septum and double cervix for further examination. Uterine malformation should be suspected if the uterus is obviously biased to one side during pregnancy, or if the uterus feels elongated, narrower in the lower part, or in abnormal fetal position, etc. Ultrasound is easier to diagnose in the early stage than in the late stage. After the diagnosis is clear, we should strengthen perinatal care and prevent various complications. In unilateral pregnancy with double uterus, vaginal delivery is possible first, but the progress of labor should be closely monitored and the indication for cesarean section should be relaxed if there is any abnormality. Bicornuate uterus Bicornuate uterus accounts for half of the abnormal uterine development. Now, according to the degree of separation of bilateral uterine horns, it can be divided into complete bicornuate uterus, that is, separated from the inner cervical opening. An incomplete bicornuate uterus is one that separates above the internal os. If there is a depression at the bottom of the uterus, it is also called bowed uterus, which is more common in clinical practice. 1.Complications during pregnancy and delivery Miscarriage, preterm delivery, abnormal fetal position and premature rupture of membranes during pregnancy in double-horned uterus are significantly higher than those in normal women, especially in bowed uterus where the chance of transverse position is higher. 2, treatment The diagnosis of double-horned uterus is not too difficult, the shape of the uterus can be seen at the bottom of the uterus is obviously depressed, in the shape of a metacarpal, the depth of the depression can be checked by ultrasound examination to determine the type of double-horned uterus. Some people believe that bicornuate uterus often has cervical insufficiency and opinions differ on whether prophylactic cervical cerclage should be performed, but cases with a history of late miscarriage and preterm labor should be checked for the presence of cervical endo-loosening and, if necessary, perform cerclage. The rate of abnormal fetal position is high in bicornuate uterus and delivery is mostly by cesarean section. Sometimes the placenta is embedded in the other corner of the uterus, and the umbilical cord should be searched along the way. In the former, the septum is from the bottom of the uterus to the inner or outer cervical opening, often combined with the vaginal septum, dividing the uterine cavity into two complete cavities; in the latter, the lower part of the septum is in any part above the inner cervical opening. It is not easy to diagnose during pregnancy because of the absence of a special uterine shape. Ultrasound can suggest a septum in the uterine cavity, and many cases are diagnosed definitely during delivery or during surgery. 1.Complications during pregnancy and delivery The same high rate of miscarriage and preterm delivery, small fetal development and abnormal fetal position exist as the above two types of malformed uterus. ultrasound examination should pay special attention to the site of placental attachment, if part or most of it is attached to the septum, it will seriously affect the blood supply and fetal oxygen supply and growth and development. If the fetus is in breech position, the fetus may ride on the mediastinum and cannot descend or the mediastinum may tear and bleed when descending. If the uterus is completely longitudinal, we should observe whether it affects the expansion of the cervical opening and relax the indications for cesarean section as appropriate to avoid damage caused by excessive stretching of the cervix by the mediastinum. If incomplete longitudinal septum is found during surgery, resection should be performed; if complete longitudinal septum is not fractured, both sides of the septum are connected with the cervix without treatment; if one side is not connected with the cervical opening, it should be removed to avoid obstruction of drainage of uterine cavity infection in the future. Four, stump angle uterus stump angle uterus can be divided into three types. Type I stumped uterus is connected to the normal uterine cavity; Type II two uterine cavities are not connected; Type III stumped uterus has no uterine cavity. The chance of pregnancy in the stumped uterus is about 1/100,000. In type I and type II, especially in type II, the fertilized egg may enter the stumped uterus without traveling from the opposite fallopian tube to the abdominal cavity to reach the opposite fallopian tube, or the egg and sperm may travel from the opposite side to the side of the stumped uterus, and then the sperm may travel from the normal side to the fallopian tube on the side of the stumped uterus and unite with the egg on that side to enter the stumped uterus. The pathway to conception can be determined by examining which side of the ovary the corpus luteum is located. Although it has been reported in the literature that about 10% of pregnancies in the stump uterus may be maintained to full term, the greatest risk is the possibility of uterine rupture at any time due to the lack of confirmation of the diagnosis. Therefore, once the diagnosis is confirmed, the principle of active management is to perform an open hysterectomy with removal of the hysterophore and the fallopian tube on that side. If the hysterophore cannot be removed due to certain circumstances, the fallopian tube on that side should not be removed or ligated in order to affect the outflow of menstrual blood in the future and to aggravate dysmenorrhea. Unicornuate uterus is one of the less common uterine malformations due to dysplasia of the myometrium and poor formation of the metaplasia, which can lead to a higher incidence of abnormalities in flow, premature pregnancy, intrauterine growth retardation placenta previa or implantation fetal position. Torsion can also occur during pregnancy due to uterine imbalance. A large proportion of deliveries require a cesarean section. VI. Vaginal longitudinal septum The caudal part of the mid-abdominal renal canal merges during fusion, but the septum does not disappear or partially disappears, and complete and incomplete longitudinal septum can occur. The mediastinum may be located medially or laterally, and in some cases it may be laterally attached to the lower vaginal wall. Longitudinal vaginal septum is often accompanied by a double uterus, a double cervix, a bicornuate uterus or a longitudinal uterus. Longitudinal septum does not interfere with conception and no complications during pregnancy occur. In the absence of other abnormalities, mediastinum does not interfere with delivery. Complete mediastinum can be pressed to one side by the fetal head. Transverse vaginal septum is a part of the vagina in which the absorption of tissue is blocked during the process of vaginalization. The absence of a central hole is rare and allows for earlier diagnosis and management due to menstrual blood retention. In the case of simple transverse septum, there is no special effect during pregnancy, but in the case of unavoidable miscarriage and cessation of embryonic development, incision is required before curettage can be performed. Transverse septum does not usually affect vaginal delivery and can be incised in a cruciform pattern as the fetal head thins with descent. Unless the septum is thick and inelastic, causing resistance to the fetal head, a cesarean section should be performed and the septum should be opened after recovery. Longitudinal or transverse vaginal septum is usually not treated during pregnancy and surgical operation can cause abortion, infection and local scar tissue formation. However, the location, thickness and elasticity of the septum should be examined and described in detail during the pregnancy examination so that it can be used as a reference when deciding on the mode of delivery. VIII. Partial vaginal atresia The lower 1/3 of the vagina is atretic in this case, which is diagnosed at an early stage because of menstrual blood storage. The vagina can be restored to patency by forming surgery, and the model must be placed for a long time after surgery, otherwise it will be easily narrowed into scar formation. If the internal genital organs are normal, conception is not affected and vaginal delivery is possible if the vaginal scar is not severe. In this case, late miscarriage or preterm delivery occurred due to cervical insufficiency caused by several cervical dilation procedures.