Can Transabdominal Cervical Length Measurement Exclude Short Cervix?

Area of Science:

• Obstetrics and Gynecology
• Diagnostic Imaging
• Fetal Medicine

Background:

• Cervical length measurement is crucial for predicting preterm birth risk.
• Transvaginal (TV) ultrasound is the standard for accurate cervical length assessment.
• Transabdominal (TA) ultrasound is a less invasive alternative, but its utility in assessing cervical length requires validation.

Purpose of the Study:

• To evaluate the efficacy of transabdominal (TA) cervical length measurement in excluding a short cervix detected by transvaginal (TV) ultrasound.
• To determine optimal TA cervical length cutoffs for ruling out short cervix.

Main Methods:

• Prospective cohort study of 404 women at 17-23 weeks gestation.
• Simultaneous TA and TV cervical length measurements were obtained.
• Short cervix defined as TV cervical length < 30 mm.

Main Results:

• TA cervical length could not be obtained in 20.6% of women.
• A TA cervical length ≥ 35 mm excluded short cervix (TV < 30 mm) with 99.5% negative predictive value.
• Using a TA cutoff of ≥ 5 mm could have potentially avoided 67.6% of TV ultrasounds.

Conclusions:

• TA cervical length of ≥ 35 mm reliably excludes a short cervix (< 30 mm).
• TA cervical length screening may not be feasible in all women but can reduce the burden of universal TV screening.
• TA ultrasound offers a potential strategy to optimize cervical length assessment in pregnancy.