Introduction/Background The physiologic change of the cervix during pregnancy and delivery may theoretically have positive influences on spontaneous regression of abnormal cervical cytology. The aim of the study is to determine the correlation between the role of delivery and the clearance of cervical cytologic abnormalities.

Methodology Unicentric retrospective study of 116 patients with cytologic abnormalities detected during pregnancy followed at Hospital 12 de Octubre (Madrid, Spain) between 2009 and 2018.

Results The mean age at diagnosis was 29.7 years (15–52). 19.8% patients were smokers, 8 had a history of sexually transmitted infection (STI) and 5 were immunocompromised. 4.3% had been vaccinated against HPV before diagnosis. The most common cervical cytologic abnormality was ASC-US in 35.3%, followed by LSIL in 34.5% and HSIL in 23.3%. High risk HPV types were detected in 53 patients. 85.3% of the patients underwent a colposcopy. In 29 cases a biopsy was performed: LSIL-CIN1 in 17.2%, HSIL-CIN2 in 13.8% and HSIL-CIN3 in 51.7% was found. 81.1% were delivered vaginally while the others by caesarean section. 90 patients underwent 6-weeks postpartum re-evaluation: clearance of HPV was 18.3% and the rate of regression of cytologic abnormalities was 44.4%. No significant difference was found between the two groups (vaginal delivery: 76 patients and caesarean section: 14 patients) according to age, race, body mass index, smoking, state of immunosuppression, history of STI or parity. Normalization of smears was shown in 45.3% women who delivered vaginally and in 40.0% women who underwent caesarean section (p=0.70).

Conclusion The role of the mode of delivery in the rate of regression of citologic abnormalities is debated. Some reports found higher rate of regression of cervical dysplasia in association with vaginal delivery compared to caesarean section, as ours does, while others showed no relationship.

Disclosure The results from this study are hypothesis generating. The higher rate of regression of cervical dysplasia in patients that delivered vaginally is in agreement with the idea that the cervical trauma generated by mechanical dilatation in labour produces an inflammatory reaction that could explain this regression phenomenon. Large population prospective studies are needed to confirm the hypothetical role of the vaginal delivery in the clearance of cervical cytologic abnormalities.