Objectives : To evaluate the accuracy of transvaginal ultrasonographic (TVS) cervical length and cervical wedging as a predictor of true preterm labour.
Study design : A prospective clinical study.
Subjects and methods : Thirty nulliparous and 43 parous women were selected among those admitted to labour ward with threatened preterm labour in King Khalid Military City Hospital, KSA, during the period from March 1996 to Feb. 1999. Patients were eligible for enrollment after they have completed the first course of parenteral tocolysis. A single TVS image of the cervix was performed. Any cervical wedging was noted and the cervical length was measured. The information thus obtained by TVS was not used in the management of the patient. Women delivered spontaneously before 36 weeks gestation were assumed to have been in true preterm labour.
Results : Seventy two patients completed the study. Twenty two subjects delivered before 36 weeks gestation. All those patients exhibited cervical wedging and shorter cervical length (< 30mm). Use of wedging as a diagnostic test for the prediction of preterm delivery had a sensitivity of 100%, a specificity of 84%, positive and negative predictive values of 73% and 100% respectively. Sonographic cervical length < 30mm yielded 100% sensitivity, 38% specificity and 41% and 100% as positive and negative predictive values respectively. Cervical sonography was specially useful in selecting women with preterm labour who would not deliver prematurely, i.e. a high negative predictive value (100%). None of the women who had no wedging and none of those whose cervical length was ≥ 30mm delivered prematurely.
Conclusion : The risk of preterm delivery is high in women whose cervical length is < 30mm and in those who exhibit cervical wedging on TVS. Cervical sonography can improve the accuracy of diagnosis in women treated for preterm labour. |
