Introduction: The primary objective of the present study is to evaluate the effect of single-layer locked versus single-layer unlocked uterine closure techniques on the development of uterine niche. The secondary objective is to evaluate the effect of the ratio of lower uterine segment (LUS) to upper uterine segment (UUS) on the development of uterine niche, which was not previously investigated in literature but which the authors consider to be a major risk factor for the development of uterine niche.
Methods: Included in this randomized study were 194 patients who were admitted to the Department of Obstetrics and Gynecology at Health Sciences University Antalya Training and Research Hospital and who underwent cesarean section (CS) due to any reason between October 2017 and May 2018. Two different techniques were used in the closure of hysterotomy: Single-layer locked continuous suturing (Group 1) and single-layer unlocked continuous suturing (Group 2). During surgery, the thicknesses of the LUS and UUS were measured using a sterile scale prior to hysterotomy closure. The patients were evaluated for the development of uterine niche at postoperative six months by transvaginal ultrasound.
Results: Control transvaginal ultrasound performed at six months after surgery revealed uterine niches in 58 out of 194 patients (29.29%; 34 patients in Group 1 [34.3%] and 24 patients in Group 2 [25.3%]). No significant difference was noted in terms of the development of uterine niche between the two groups (p = .167). The mean LUS and UUS in patients without uterine niche development were 6.81 ± 1.26 mm and 9.38 ± 1.26 mm, whereas the mean LUS and UUS in patients with uterine niche development were 4.24 ± 1.15 mm and 9.21 ± 2.15, respectively (p = .001 and p = .236). The mean UUS/LUS ratio is 1.4 ± 0.16 among patients without uterine niche and 2.21 ± 0.31 in patients with uterine niche (p < .001).
Conclusions: The present study found no statistically significant difference in niche size between the two groups. However, the study reports that the ratio of upper to lower uterine segment that was not previously investigated in literature is a major risk factor for the development of uterine niche.
Keywords: Cesarean scar defect; niche risk factors; uterine diverticulum; uterine niche; uterine scar defect.