Outcome of pregnancy after laser conization: implications for infection as a causal link with preterm birth

To investigate a causal link between infection and preterm birth in women with a shortened cervix induced by prior laser conization.

We conducted a retrospective review of the outcomes of 47 singleton pregnancies with a history of laser conization. Cervical length was measured between 17 and 23 weeks of gestation. Receiver-operating characteristic curves were used to determine the best cut-off point for the cervical length for predicting spontaneous preterm birth. We measured infectious markers in 12 women who had experienced preterm labor.

Nine women had had premature labors and three had had late abortions. The mean +/- SD cervical length was 33.1+/-9.1 mm. The optimal cut-off for predicting preterm delivery was 25 mm with a sensitivity and specificity of 75.0% and 97.1%, respectively. Concentrations of granulocyte elastase were positive in five of the six samples determined. The white blood cell count and C-reactive protein levels were elevated in four out of the six patients. Sixty-seven percent of the vaginal cultures were positive for bacteria. Chorioamnionitis was present in seven women.

For the prediction of preterm birth in patients with a history of conization, it is helpful to look for signs of local infection when the cervical length is less than 25 mm.