OBJECTIVE. The 2006 American Society for Colposcopy and Cervical Pathology Consensus guidelines state that it is acceptable to defer colposcopy until 6 weeks postpartum in pregnant patients with atypical squamous cells of undetermined significance (ASC-US) or low-grade squamous intraepithelial lesion (LSIL) cytology. Therefore, we sought to determine the incidence of cervical intraepithelial neoplasia (CIN) 2,3 in pregnant patients referred to a university colposcopy clinic. MATERIALS AND METHODS. A retrospective study identified all pregnant women with abnormal cytology referred to the University of Alabama at Birmingham colposcopy clinic between May 2005 and September 2007. After an institutional review board approval was obtained, demographic information, referral cytology, and histologic data were collected. The colposcopic impression was also obtained from the records. RESULTS. Six hundred twenty-five pregnant patients were identified. The mean age was 23 years (range, 14-44 years), the mean parity was 1 (range, 0-7), and the mean gestational age was 24 weeks (range, 4-39 weeks). The most common referral cytology was LSIL (41.0%), followed by ASC-US (34.1%), and high-grade squamous intraepithelial lesion (13.6%). One hundred thirty-eight patients (22%) underwent cervical biopsy at the time of initial colposcopy. Forty-three patients had CIN 1, 28 patients had CIN 2, and 23 patients had CIN 3. Forty-four patients (32%) had no evidence of CIN on biopsy. There were no cases of invasive cervical cancer identified. Of the 469 patients with ASC-US and LSIL cytology, 20 of 78 patients who had a cervical biopsy were diagnosed with CIN 2,3. Of the 128 patients with high-grade intraepithelial lesion or high-grade squamous intraepithelial lesion cytology, 31 of 60 patients who had a cervical biopsy were diagnosed with CIN 2,3. Repeat colposcopy in the third trimester was performed on 47 patients. Only 3 of 13 patients with a repeat biopsy had CIN 2,3. CONCLUSIONS. Pregnant patients with ASC-US or LSIL cytology rarely have colposcopically suspected CIN 2,3 at their initial colposcopy that warrants a cervical biopsy; therefore, it is reasonable to defer the initial colposcopy in patients with ASC-US and LSIL until at least 6 weeks postpartum. ©2009The American Society for Colposcopy and Cervical Pathology.