OBJECTIVE: Our purpose was to determine whether prenatal colposcopy is beneficial in pregnant women with squamous atypia, atypical squamous cells of undetermined significance, or low-grade squamous intraepithelial lesions on an initial screening Papanicolaou smear. STUDY DESIGN: A retrospective chart review identified a cohort of pregnant patients referred to the colposcopy clinic at Carolinas Medical Center between October 1991 and December 1994 with squamous atypia, atypical squamous cells of undetermined significance, or low-grade squamous intraepithelial lesions. Results of the colposcopic examination, cervical biopsy specimens, postpartum evaluation, and postpartum treatment were recorded. Descriptive statistics were used to tabulate numbers and percentages for all variables with 95% confidence intervals to determine disease progression. RESULTS: Prenatal colposcopy was performed on 253 women during the study period. The colposcopic impression was normal or consistent with low-grade squamous intraepithelial lesions in 235 (93%) of the women. Of the 67 women who had a cervical biopsy, 6 had a histologic diagnosis of high-grade squamous intraepithelial lesions. Postpartum Papanicolaou smears were obtained in 224 patients; 71 (32%) were normal, 145 (65%) were unchanged, and 8 (3%) showed high-grade squamous intraepithelial lesions. Of the 69 patients who had a postpartum cervical biopsy, 4 were found to have high-grade squamous intraepithelial lesions. Eight of the 10 women with biopsy-proved high-grade squamous intraepithelial lesions were compliant with treatment after delivery. Histologic examination of the cervix with tissue obtained by either loop conization or cold knife conization showed no evidence of invasive carcinoma. CONCLUSION: Squamous atypia, atypical squamous cells of undetermined significance, or low-grade squamous intraepithelial lesions on a Papanicolaou smear in a pregnant patient does not require colposcopic evaluation during pregnancy. Progression of low-grade dysplasia to carcinoma during pregnancy is unusual, and no patient in this study was found to have invasive cancer. (Am J Obstet Gynecol 1997;177:298-302.)