A comparison of ultrasonographically detected cervical changes in response to transfundal pressure, coughing, and standing in predicting cervical incompetence.

OBJECTIVE

Our purpose was to compare various noninvasive stress techniques for their ability to elicit ultrasonographic cervical changes and to determine their efficacy in detecting ultrasonographic cervical incompetence.

STUDY DESIGN

Eighty-nine patients at risk for pregnancy loss and preterm birth underwent ultrasonographic evaluation of the cervix at least twice between 15 and 24 weeks of gestation. With use of a transvaginal probe, the funnel width, funnel length, and endocervical canal length were measured in millimeters with the patient in the supine position. These measurements were repeated after three stress tests: transfundal pressure, coughing, and standing. The difference between the baseline measurements and those obtained after the stress tests were determined. A positive response to stress was defined as any decrease in endocervical canal length accompanied by an increase in funnel width and length. Improvement was defined by any increase in endocervical canal length accompanied by a decrease in funnel width and length. Cervical incompetence was defined as the presence of progressive cervical changes on ultrasonographic examinations with final endocervical canal length measurements below 26 mm. Results are reported as median (range).

RESULTS

The number of positive cervical responses to transfundal pressure (19%, 17/89) was significantly greater than to coughing (3.3%, 3/89) and standing (9.0%, 8/89). The status of the cervix improved with standing in three cases, whereas this was not seen with transfundal pressure or coughing. There was no case where there was a positive response to standing or coughing and not to transfundal pressure. When the changes in funnel width and length and endocervical canal length as a result of transfundal pressure and standing in the 17 cases that responded to transfundal pressure, transfundal pressure resulted in a significantly greater increase in funnel width and length and a decrease in endocervical canal length. The efficacy of transfundal pressure in detecting the cervix that had subsequent progressive changes on ultrasonography was as follows: sensitivity 83.3%, specificity 97.2%, and positive and negative predictive values 88.2% and 95.8%, respectively. The efficacy of coughing was sensitivity 16.7%, specificity 100%, and positive and negative predictive values 100% and 85.5%, respectively. The efficacy of standing was sensitivity 33.3%, specificity 97.2%, and positive and negative predictive values 75% and 85.2%, respectively. Similar results were obtained when the analysis was confined to 37 patients who had a prior history of a midtrimester miscarriage.

CONCLUSION

Transfundal pressure was the most effective technique in eliciting cervical changes during the active assessment of the cervix during pregnancy and the most sensitive in detecting the cervix that had progressive second-trimester cervical shortening during pregnancy, compared with coughing or standing position.