Cervical intraepithelial neoplasia, referred to as cervical CIN, is a group of precancerous lesions closely related to cervical invasive carcinoma and cervical cancer, which reflects the continuous process in the development of cervical cancer. I. Etiology of cervical CIN Epidemiological investigations have found that CIN is closely related to sexual disorders and smoking. Other risk factors include early sexual life (<16 years), sexually transmitted diseases (especially HPV infection), low economic status, oral contraceptives and immunosuppression. The relationship between HPV infection and CIN is currently well studied. More than 90% of CIN have HPV infection, compared to only 4% of normal cervical tissue. In early HPV infection, the diseased cervical epithelium becomes typically pectus excavatum, and HPV infection does not persist and is often suppressed or disappears spontaneously. Many women with HPV have no clinical symptoms. When HPV infection persists, CIN can be induced by other factors (e.g., smoking, use of birth control pills, sexually transmitted diseases, etc.) HPV testing is not routinely performed in women under 30 years of age. CINI is primarily associated with HPV 6, 11, 31, and 35, and is often a mixed infection with multiple subtypes of HPV. CINII and CINIII are mainly associated with HPV 16, 18, 33, 58. The diagnosis of CIN should follow a "three-step" diagnostic procedure of cytology (TCT and HPV), colposcopy and histopathological examination. Cervical biopsy is the most reliable method to diagnose CIN. Any lesion visible to the naked eye should be biopsied at a single or multiple points. If there is no obvious lesion, biopsy at points 3, 6, 9 and 12 of the cervical migratory zone can be chosen or taken under colposcopic guidance in the uncolored area of the iodine test to improve the diagnostic rate. Third, treatment of cervical CIN 1, high-risk HPV infection (except 16 and 18), TCT negative or ASC-US: recheck TCT after 6 months; recheck TCT and HPV after 1 year. HPV 16 and 18 positive, even if TCT is normal, colposcopic biopsy is recommended. 2. ASC-H, cervical biopsy is required; AGC (atypical glandular cells) requires cervical biopsy and segmental scraping. If pathological results exclude other lesions, review after six months or a year. 3, CINI 60%-80% will naturally regress, the current treatment of CINI tends to conservative treatment. CINI can be treated with laser, microwave and cryotherapy, and also with LEEP treatment. CIN2 lesions are more heterogeneous than CIN3, and long-term follow-up reveals a greater likelihood of regression, but the histological distinction between CIN2 and CIN3 is extremely difficult, so to improve safety, CIN2 is used as the starting point of treatment.CIN2 can be treated with laser, microwave, cryotherapy, LEEP or conization.CIN3 total hysterectomy for those without fertility requirements; total hysterectomy for young, fertile people. CIN2 can be treated with laser, microwave, cryotherapy or LEEP or conization. Some scholars now suggest that hysterectomy should not be used as the primary or initial treatment for CIN2 and CIN3. After treatment of CIN2 and CIN3, HPV can be detected at intervals of 6-12 months, or cytology alone or in combination with cytology and colposcopy at 6-month intervals. During pregnancy, excessive estrogen causes the columnar epithelium to migrate out to the vaginal part of the cervix, and the basal cells in the migratory zone develop atypical hyperplasia, which can resemble carcinoma in situ; they are also susceptible to HPV infection due to low resistance. There is no evidence that CIN is more likely to develop into cervical invasive carcinoma during pregnancy than during non-pregnancy. Most lesions resolve spontaneously or do not progress after delivery, so it is generally accepted that CIN during pregnancy can be managed conservatively. Cervical conization should only be performed when there is a high suspicion of invasive cancer.