Prospective evaluation of a protocol for using transabdominal ultrasound to screen for short cervix

Autor: Alan Fishman, Kimberly Mallory, C. Andrew Combs, Sarah Y. Lee, Santosh Pandipati, Francesca Ianovich
Rok vydání: 2014
Předmět:
Zdroj: American journal of obstetrics and gynecology. 213(1)
ISSN: 1097-6868
Popis: Objective We sought to evaluate a recently proposed protocol whereby transabdominal ultrasound of the cervix might be used as a prescreen to select women to undergo or to forgo measurement of cervical length via transvaginal ultrasound (CL vag ). Study Design This was a prospective cohort study. Measurements of cervical length via transabdominal ultrasound (CL abd ) and CL vag were made in women with singleton pregnancy during routine obstetrical ultrasound examination at 18 0/7 to 23 6/7 weeks of gestation. The transabdominal screen was considered positive if CL abd was ≤36 mm with the maternal bladder full or ≤35 mm with the bladder empty, or adequate imaging of the cervix could not be obtained. Sensitivity, specificity, predictive values, and likelihood ratios of a positive screen to detect a short cervix (CL vag ≤25 mm) were calculated. Results An interim analysis identified several technical problems with CL abd measurements, so the protocol was extensively revised. Under the revised protocol, 1580 women were included. Adequate views of the cervix were obtained via transabdominal imaging in 46% of subjects with the bladder empty and 56% with the bladder full. The correlation between CL abd and CL vag was poor (r = 0.38). Of the 17 patients with a short cervix, 15 had suboptimal transabdominal exams (screen positive) and 2 had CL abd ≤35 mm with bladder empty (screen positive). Sensitivity of the screen was 100% (95% confidence interval, 80.5–100%) but specificity was only 32.2% (95% confidence interval, 29.9–34.6%) and screen positive rate was 66.3%. Several technical problems and limitations of transabdominal imaging of the cervix are shown. Conclusion Using modern, high-resolution ultrasound equipment, we were unable to adequately image the cervix via transabdominal ultrasound in half the cases. Although we confirmed that a CL abd cutoff value of 35-36 mm is appropriate for detection of short cervix, the technique for measuring CL abd is fraught with technical problems. Practitioners must validate the technique in their own practice before adopting this or similar prescreening protocols. We decided not to adopt this protocol.
Databáze: OpenAIRE
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