Ultrasonographic Monitoring of Scarred Lower Uterine Segment during Pregnancy

This paper discusses evaluation of Trans-Abdominal Ultra-Sound (TAUS) for the diagnosis of defects or abnormal thinning in the scarred lower uterine segment during 3rd trimester of pregnancy done as near to expected date of delivery (EDD) as possible so that selection of women for a trial of labor for vaginal birth after Caesarean Section (C-Section) (TOL-VBAC) can be done. The study population consisted of 103 women attending the antenatal clinic of this hospital. Of these, 22 were primigravidae (control group) and 81 were multi gravidae with 1 previous Lower Segment C-Section (LSCS) (test group). Each study included multiple measurements of the thickness of the anterior wall of Lower Uterine Segment (LUS) both in longitudinal and transverse sections. Minimum three readings were taken. An average of these was taken to be the thickness of LUS. Any asymmetry of the thickness of the LUS resulting in wedge defect was made. Patients were followed up to the time of delivery. Those delivered by LSCS were considered for the final analysis. During LSCS, the thickness of LUS was measured. The Ultrasound (U/s) and laparotomy findings were compared and the test parameters of TAUS were calculated. Positive and negative predictive value was 100%. An LUS with sonographic wall thickness < 3mm is abnormally thin. Study results suggest that TAUS is safe and reliable test with a high degree of specificity and sensitivity to diagnose defects, ballooning, and abnormally thin lower uterine segment. This will help obstetricians in deciding which patient may be allowed a TOL-VBAC.