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

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