The objective of this work was to assess proper management of squamous intraepithelial lesion (SIL) and microinvasive carcinoma during and after pregnancy, to assess risks of punch biopsy and conization in pregnancy and to assess regression, persistence and risk of progression with low-grade (L) and high-grade (H) SIL.We carried out a prospective study of 167 pregnant women from our colposcopic unit who were referred to us for abnormal cytological findings between 1997 and 2002. The diagnosis of precancerosis was verified in all of the women by punch biopsy, suspect microinvasive carcinoma needle or LETZ conization up to the 20th week of pregnancy. All women were followed-up during the pregnancy and 24 months after their deliveries.In 23 women with suspect early invasion we performed conization during the pregnancy (weeks 13-23). There were six cases (26.1%) of microinvasive carcinoma and 17 cases (73.9%) of HSIL. One pregnancy aborted two days after the conization. No other obstetrical complications were recorded and there were no premature deliveries. Sixty-two women with HSIL were only followed-up during their pregnancy. We observed complete regression of HSIL during the study in 14 patients (22.6%), regression to LSIL in 17 patients (27.4%), persistence in 25 patients (40.3%) and progression to microcarcinoma in six cases (9.7%). Eighty-two patients were followed up for LSIL. Complete regression of LSIL was observed during the study in 40 cases (48.8%), persistence in 24 cases (29.2%) and progression to HSIL in 18 cases (22.0%).For LSIL and HSIL during pregnancy the above follow-up is a sufficient and safe protocol. Suspect microinvasive carcinoma should be treated by conization, which is a safe procedure until the 24th week of pregnancy.