The natural history of a positive response to transfundal pressure in women at risk for cervical incompetence.

OBJECTIVE

Our purpose was to observe the evolution of the endocervical canal length in women at risk for cervical incompetence after a positive response to transfundal pressure.

STUDY DESIGN

Ten women at risk for cervical incompetence had a midtrimester cervical evaluation with transvaginal ultrasonography and transfundal pressure. With a transvaginal probe, the endocervical canal length was first measured. Transfundal pressure was then applied and the endocervical canal length was remeasured. All patients had a positive response to transfundal pressure as defined by a decrease in endocervical canal length after application of transfundal pressure. At the initial evaluation the digital examination of the cervix had revealed a closed and long cervix in all 10 cases. In 9 of the 10 patients repeat examinations were performed until the endocervical canal length progressively shortened to <10 mm or the digital examination revealed a dilated cervix. The endocervical canal lengths after application of transfundal pressure from the first and last examination were compared. One patient was lost to follow-up, but the obstetric outcome was available.

RESULTS

The median time interval between the first and final examination was 7 (2 to 20) days in 9 of the patients. The median (range) gestational age at the first and final examination was 19.0 (15 to 22) weeks (n = 10) and 20.5 (18 to 24) weeks (n = 9), respectively. There was significant shortening of the endocervical canal length from the first to the last examination; 12.2 (4 to 20) mm (n = 10) versus 0.0 (0 to 9.5) mm (n = 9), p = 0.008. Six patients had membranes at the external cervical os before application of transfundal pressure at the last examination. The one patient lost to ultrasonographic follow-up had a pregnancy loss at 23 weeks of gestation, 6 weeks after a positive response to transfundal pressure.

CONCLUSION

In patients at risk for cervical incompetence, shortening of the endocervical canal length in response to transfundal pressure requires treatment with a cervical cerclage because it is associated with progressive cervical changes over 1 to 3 weeks.