1. Diagnosis of vaginal atresia: In order to improve the typing and diagnosis of the disease, it is suggested that the untyped upper vaginal atresia and apical vaginal atresia should be classified as type III and type IV respectively after type I and type II. According to the anatomical features, type Ⅰ: refers to lower vaginal atresia; type Ⅱ: refers to complete vaginal atresia; type Ⅲ: refers to upper vaginal atresia; type Ⅳ: refers to apical vaginal atresia. 2. Vaginal atresia and its occurrence: In 1976, Simpson suggested that vaginal atresia is different from congenital absence of the vagina, in that the former is caused by defects in the development of the genitourinary sinuses, and the uterine body is mostly normal and may be combined with cervical dysplasia, whereas the latter is the result of mullerian duct dysplasia, which is manifested by the absence of both the uterus and the vagina. The Mayer-Rokitansky-Kunster-Hauser (MRKH) syndrome is a female genital tract anomaly due to the development of the head segment of the Mullerian ducts to form the fallopian tubes without the development of their middle and caudal segments, which is characterized by the absence of a uterus and vagina and may be associated with renal and skeletal anomalies, whereas vaginal atresia is due to the fusion of the bilateral Mullerian ducts to form the vagina. It is associated with cervical atresia, and the endometrium may have normal secretory function. In type I vaginal atresia, the urogenital sinus is not involved in the formation of the lower vaginal segment due to normal development of the urogenital sinus, and the lower vaginal segment is atretic, while the upper vaginal segment and uterus are normally developed. Type III vaginal atresia, in which the urogenital sinus is normally developed and the nodule of the müllerian duct is not cavernous, may be combined with abnormal development of the external division and/or fusion of the müllerian duct, and presents with complete vaginal atresia with cervical atresia and normal or malformed development of the uterine body. In type IV vaginal atresia, the fused and/or external divisions of the müllerian ducts are involved, while the müllerian nodes and sinus vaginal bulb are still normally developed, showing apical vaginal atresia with cervical atresia and normal or malformed development of the uterine body. 3. Female genital tract development: It is now recognized that a pair of Mullerian ducts develop into the fallopian tubes, uterine body, cervix and upper part of the vagina, and the urogenital sinuses develop into the lower part of the vagina and external genitalia. How exactly does development occur? The traditional theory of embryonic development cannot fully explain all types of vaginal atresia. (1) Two new hypotheses: In recent years, the traditional theory of female genital tract development has been supplemented by the embryogenesis hypothesis of Muller et al. which suggests that the fusion of the middle and caudal segments of the Mullerian ducts is a separate process, starting in the middle part, at the level of the uterine isthmus, followed by fusion and resorption towards both ends. The hypothesis of Muller et al. was confirmed by experiments: Sánchez-Ferrer et al. observed that in female mouse embryos, the müllerian ducts grew caudally while converging towards the midline, forming a cross between the medial müllerian ducts at 15 days after conception, after which the cohesive ends of the two müllerian ducts met and fused. The caudal end of the merged portion of the two ducts grows laterally until it joins and fuses with the distal epithelium of the lateral nocturnal duct. Accordingly, Acién et al. and Sánchez-Ferrer et al. divided the müllerian ducts into three parts, namely the cohesive, fused, and external divisions, corresponding to the oviduct and body of the uterus, the isthmus, and the cervical canal, respectively. The nodule was formed by the outer division of the mullerian duct with the apex of the mullerian duct and the base of the pair of sinus vaginal bulbs, flanked by the nonungual duct and the urogenital sinus anteriorly. Therefore, the hypothesis that the end of the mullerian ducts and the nodules of the mullerian ducts are relatively independent in structure is proposed. This could explain cases with abnormal uterine development but with a vagina with a blind end but normal depth and breadth. (2) Two hypotheses: The traditional theory of embryonic development and the above hypothesis cannot explain cases of atresia of the apical vagina combined with primordial uterus and complete atresia of the vagina combined with type IV cervical atresia, which are cases of staged hypoplasia of the malleolus. Therefore, it is hypothesized that the development of the malleolus is not only sequential, but also time-limited, i.e., only a certain amount of development can take place in a certain embryonic time period, and if the development of the malleolus is stalled in a certain time period, it can only take place in the next time period when the disturbing factors are removed in the next time period. In addition, the development of the vaginal plate and luminalization are sometimes limited, and the development of the vaginal epithelium is influenced by estrogen because the follicles start to develop and produce a small amount of estrogen in the last 6 weeks of pregnancy, and estrogen levels are higher in female fetuses than in male fetuses. This may explain why in type I vaginal atresia, the genitourinary sinus does not penetrate the vaginal cavity, but the upper vaginal mucosa is still compound squamous epithelium. (3) Diagnosis and treatment: Vaginal atresia is usually combined with cervical atresia, which is characterized by periodic lower abdominal pain and pelvic mass formation during puberty without menarche. The treatment plan should be designed according to the development of the uterus: type I vaginal atresia can be treated by surgical opening of the vaginal channel and epithelialization; type IV vaginal atresia combined with primordial uterus does not require treatment; type II and III vaginal atresia combined with primordial uterus can be treated by vaginoplasty before marriage; type II, III and IV vaginal atresia combined with cervical atresia should be treated according to the cervical atresia typing to decide the timing of uterus removal and vaginoplasty. Type I cervical atresia can be treated by preserving the uterus and performing cervical and vaginoplasty via the perineal route alone; type II and III cervical atresia should be treated by hysterectomy first and then vaginoplasty 3-6 months before marriage; type IV cervical atresia can be treated by either hysterectomy first and then vaginoplasty 3-6 months before marriage, or vaginoplasty and cervicoplasty via the perineal route, according to the request of the affected party. The atresia can be treated according to the request of the affected party.