OBJECTIVE To observe the behavior of cervical intraepithelial neoplasia in pregnant adolescents and the persistence before the delivery. MATERIALS AND METHODS A cross-sectional study including 47 pregnant adolescents with NIC-positive results diagnosed by colposcopy during pregnancy with subsequent evaluation before the delivery. Nonrandom sampling of consecutive cases. Descriptive statistics with central and dispersal measures. RESULTS In total, 156 pregnant adolescents were studied, of which 30% (n = 47) had positive results to NIC with subsequent evaluation. Ages 18 ± 1.5 years, primiparous 77%, sexual activity initiation 15.6 ± 1.6 years old, sexual partners 1 (1-6), smoking and alcoholism 21%. At the beginning of pregnancy, 98% had NIC I results and 2% had NIC II by colposcopy. After delivery, 13% had normal results and 87% remained in NIC I. CONCLUSION The findings suggest that in pregnant adolescents there exists a natural dysplasia history as in pregnant women. Most of the lesions are NIC I and don't modify the evolution, with some regressing after the delivery.