Sonographic lower uterine segment thickness and risk of uterine scar defect: a systematic review.
OBJECTIVE
To study the diagnostic accuracy of sonographic measurements of the lower uterine segment (LUS) thickness near term in predicting uterine scar defects in women with prior Caesarean section (CS).


METHODS
PubMed, Embase, and Cochrane Library (1965-2009).


METHODS
Studies of populations of women with previous low transverse CS who underwent third-trimester evaluation of LUS thickness were selected. We retrieved articles in which number of patients, sensitivity, and specificity to predict a uterine scar defect were available.


RESULTS
Twelve eligible studies including 1834 women were identified. Uterine scar defect was reported in a total of 121 cases (6.6%). Seven studies examined the full LUS thickness only, four examined the myometrial layer specifically, and one examined both measurements. Weighted mean differences in LUS thickness and associated 95% confidence intervals between women with and without uterine scar defect were calculated. Summary receiver operating characteristic (SROC) analysis and summary diagnostic odds ratios (DOR) were used to evaluate and compare the area under the curve (AUC) and the association between LUS thickness and uterine scar defect. Women with a uterine scar defect had thinner full LUS and thinner myometrial layer (weighted mean difference of 0.98 mm; 95% CI 0.37 to 1.59, P = 0.002; and 1.13 mm; 95% CI 0.32 to 1.94 mm, P = 0.006, respectively). SROC analysis showed a stronger association between full LUS thickness and uterine scar defect (AUC: 0.84 +/- 0.03, P < 0.001) than between myometrial layer and scar defect (AUC: 0.75 +/- 0.05, P < 0.01). The optimal cut-off value varied from 2.0 to 3.5 mm for full LUS thickness and from 1.4 to 2.0 for myometrial layer.


CONCLUSIONS
Sonographic LUS thickness is a strong predictor for uterine scar defect in women with prior Caesarean section. However, because of the heterogeneity of the studies we analyzed, no ideal cut-off value can yet be recommended, which underlines the need for more standardized measurement techniques in future studies.
Jastrow
Nicole
N
Department of Obstetrics and Gynaecology, Centre Hospitalier Universitaire Sainte-Justine, Faculty of Medicine, Université de Montréal, Montreal QC.
Chaillet
Nils
N
Department of Obstetrics and Gynaecology, Centre Hospitalier Universitaire Sainte-Justine, Faculty of Medicine, Université de Montréal, Montreal QC.
Roberge
Stéphanie
S
Department of Social and Preventive Medicine, Faculty of Medicine, Université Laval, Quebec QC; Department of Obstetrics and Gynaecology, Centre de recherche du Centre Hospitalier Universitaire de Québec (CRCHUQ), Faculty of Medicine, Université Laval, Quebec QC.
Morency
Anne-Maude
AM
Department of Obstetrics and Gynaecology, Faculty of Medicine, McGill University, Montreal QC.
Lacasse
Yves
Y
Institut Universitaire de Cardiologie et de Pneumologie, Hôpital Laval, Faculty of Medicine, Université Laval, Quebec.
Bujold
Emmanuel
E
Department of Obstetrics and Gynaecology, Centre Hospitalier Universitaire Sainte-Justine, Faculty of Medicine, Université de Montréal, Montreal QC; Department of Social and Preventive Medicine, Faculty of Medicine, Université Laval, Quebec QC; Department of Obstetrics and Gynaecology, Centre de recherche du Centre Hospitalier Universitaire de Québec (CRCHUQ), Faculty of Medicine, Université Laval, Quebec QC.
D002585:Cesarean Section / Q000009:adverse effects*; D002921:Cicatrix / Q000150:complications*; D005260:Female; D006801:Humans; D011247:Pregnancy; D014463:Ultrasonography; D014597:Uterine Rupture / Q000517:prevention & control; D014599:Uterus / Q000000981:diagnostic imaging*