[Does Lower Uterine Segment Thickness Measurement Improve Birth Planning After Previous Cesarean Section?]

Area of Science:

• Obstetrics and Gynecology
• Maternal-Fetal Medicine
• Diagnostic Imaging

Background:

• Lower uterine segment (LUS) thickness measurement is commonly used for selecting patients for trial of labor after cesarean section (TOLAC).
• Current evidence lacks proof of significant benefit, standardized protocols, or clear cut-off values for LUS measurement.
• This study aimed to assess the practical benefit of LUS thickness measurement in routine clinical practice.

Purpose of the Study:

• To evaluate the clinical utility and accuracy of lower uterine segment (LUS) thickness measurements.
• To determine the effectiveness of ultrasound in detecting uterine defects in pregnancies with prior cesarean section (CS).
• To assess the diagnostic performance of LUS measurements at various cut-off values.

Main Methods:

• Retrospective analysis of 631 pregnancies following a previous cesarean section (CS).
• Ultrasound measurements of myometrial (mLUS) and full LUS (fLUS) thickness were performed in 399 patients.
• Analysis included incidence, timing, and mode of uterine defect detection, along with sensitivity, specificity, PPV, and NPV calculations.

Main Results:

• Uterine defects were identified in 4.4% of patients.
• Ultrasound detection rates for uterine defects were low at 13.6%.
• Lower cut-off values (2mm fLUS / 1mm mLUS) demonstrated superior diagnostic performance (Sensitivity: 75%, Specificity: 96%, PPV: 48.3%, NPV: 98.7%) compared to higher values.

Conclusions:

• The clinical benefit of lower uterine segment (LUS) thickness measurement appears overestimated.
• Methodological factors contribute to inaccuracy; a standardized protocol with both transabdominal and transvaginal scans by trained personnel may improve accuracy.
• Exclusion of uterine defects may be a more valuable tool for prenatal selection in women with a history of cesarean section.