Ultrasonographic Evaluation of Lower Uterine Segment to Predict the Integrity and Quality of Cesarean Scar during Pregnancy: A Prospective Study.

Abstract

A prospective randomized study was conducted to measure the serial thickness of the lower uterine segment (LUS) by transvaginal ultrasonography in a control group of 80 women having no history of uterine surgery and in a study group of 43 women having a history of previous cesarean section (C/S). In the study group, more than 2 mm of thickness of the LUS was considered as good healing and less than 2 mm of thickness as poor healing. After serial sonographic examination, the women with good healing were given trial for labor unless an obstetrical indication for C/S existed. The appearance of the LUS during surgery was compared with antenatal ultrasonographic assessment by direct inspection. Twenty two (79%) of 28 women with a well healed scar had trial labor with the result that 46% had a successful vaginal birth without any uterine rupture of dehiscence. Eight women with poor healing all had elective C/S. Seven women with a 2 mm LUS thickness were individually categorized for delivery mode. Two of those women delivered vaginally. The LUS was found to be thin to translucent in these later two groups. Two mm or less as a criterion for poor healing had the sensitivity and specificity of 86.7% and 100% respectively. The positive predictive value was 100% and the negative predictive value was 86.7%. Ultrasonographic evaluation is effective in predicting the quality of a uterine scar and in differentiating the risk group of probable uterine rupture from the non risk group.

Sonographic Evaluation of the Lower Uterine Segment in Patients With Previous Cesarean Delivery

“…Our finding of a difference in LUS thickness between the cesarean and control groups is similar to the findings of Gotoh et al 9 and Qureshi et al, 13 which showed that the LUS was thinner in women with previous cesarean delivery than in the control groups. However, the parity factor had not been examined in those studies.…”

“…It is therefore obvious that the techniques used for measuring the LUS thickness and identifying uterine defects have not been consistent among different studies. Although some studies seem to give good results with different measurement techniques, 11,13,15 our experience suggests that measurement of only the myometrial layer should be more representative of the LUS thickness because 13.2% of our patients showed thickening of the LUS scar at the outer layer but thinning of the underlying myometrial layer. In addition, measurements that include the bladder mucosa and the underlying tissues are more likely influenced by the variation of the bladder size.…”

Sonographic Prediction of Scar Dehiscence in Women with Previous Cesarean Section

“…At the opening of the abdominal wall during CS, surgeon made an objective evaluation of the integrity and thickness of the LUS, as described by Qureshi et al [13]. The LUS was graded as follows: Grade I (LUS was well developed), Grade II (LUS was thin without visible content), Grade III (LUS was translucent with visible content), and Grade IV (LUS had well-circumscribed defects, either dehiscence or rupture).…”

“…Based on the previous studies [13][14][15][16], a sample size of 34 women in each group was required to compare the difference in mean LUS thickness, for an a of 0.05 and a power of 0.80, with an anticipated difference in mean LUS thickness of 0.4 mm and an anticipated SD of 0.8 mm. Considering 10 % rate of spontaneous labor before surgery and any loss to follow up, a total of 50 women were selected in each group.…”

“…Although the correlation between interdelivery interval and grades of LUS (II-IV) approached significance (p = 0.062), it was not statistically significant probably due to less number of women (n = 7). A definite technique for use of ultrasound for measurement of LUS and myometrium needs to be standardized (as per Jastrow et al [9] ), filling of urinary bladder before sonography (Bujold et al [12]), and grades of LUS (Qureshi et al [13]), and training module for obstetricians and sonologists should be offered for assessment of LUS and myometrium.…”