or destruction of the abnormal cervical cells by cryocautery, electrocautery, laser cautery, loop electrical excision procedure (LEEP), or cervical conization. The typical threshold for treatment is CIN 2+, although a more restrained approach may be taken for young persons and pregnant women. A Cochrane review found no clear evidence to show which surgical technique may be superior for treating CIN. Evidence suggests that while retinoids are not effective in preventing the progression of CIN, they may be effective in causing regression of disease in people with CIN2. Therapeutic vaccines are currently undergoing clinical trials. The lifetime recurrence rate of CIN is about 20%, but it isn't clear what proportion of these cases are new infections rather than recurrences of the original infection. Research to investigate if prophylactic antibiotics can help prevent infection in women undergoing excision of the cervical transformation zone found a lack of quality evidence. Surgical treatment of CIN lesions is associated with an increased risk of infertility or subfertility. A case-control study found that there is an approximately two-fold increase in risk i. The findings of low quality observational studies suggest that women receiving treatment for CIN during pregnancy may be at an increased risk of premature birth. People with HIV and CIN 2+ should be initially managed according to the recommendations for the general population according to the 2012 updated ASCCP consensus guidelines. Outcomes It used to be thought that cases of CIN progressed through grades 1–3 toward cancer in a linear fashion. However most CIN spontaneously regress. Left untreated, about 70% of CIN 1 will regress within one year; 90% will regress within two years. About 50% of CIN 2 cases will regress within two years without treatment. Progression to cervical carcinoma in situ (CIS) occurs in approximately 11% of CIN 1 and 22% of CIN 2 cases. Progression to invasive cancer occurs in approximately 1% of CIN 1, 5% of CIN 2, and at least 12% of CIN 3 cases. Progression to cancer typically takes 15 years with a range of 3 to 40 years. Also, evidence suggests that cancer can occur without first detectably progressing through CIN grades and that a high-grade intraepithelial neoplasia can occur without first existing as a lower grade. Research suggests that treatment does not affect the chances of getting pregnant but it is associated with an increased risk of miscarriage in the second trimester. Epidemiology Between 250,000 and