The objective of this study was to evaluate a minimal laser conization procedure during pregnancy for safe diagnosis and treatment of carcinoma in situ. This was a clinical prospective study in a University Hospital. Seventy-five pregnant women selected on the basis of a cervical smear showing carcinoma in situ or dysplasia, or an extensive picture confirmed by colposcopy, were referred for minimal conization procedure. A free-hand minimal conization procedure using a carbon dioxide (CO2) laser was performed in ambulant care under local anaesthesia. The minimal conization procedure is defined as the removal of a 7.0 mm high, slightly conical tissue specimen from the uterine cervix containing the entire transformation zone. After the cone specimen was taken, routine cervical curettage was also performed. There were no complications attributable to the conization procedure and no adverse effects either during pregnancy or at delivery. Histopathological examination of the cone specimens from 75 patients revealed carcinoma in situ or dysplasia in 65 cases. More advanced malignancy was found in 10 cases; micro-invasive carcinoma stage 1A (n = 7) or stage 1B (n = 3). The minimal conization procedure with CO2 laser during pregnancy enables safe diagnosis of carcinoma in situ selected by cytology and colposcopy. It also proved useful for diagnosis and treatment of stage 1A or stage 1B carcinoma, enabling pregnancy to be preserved and radical cancer treatment to be postponed until delivery.