Aetiology, risk factors and preventive strategies for niche development: A review.

The increase in caesarean sections (CS) has resulted in an increase in women with a uterine niche. The exact aetiology of niche development has yet to be elucidated but is likely multifactorial. This study aimed to give a systematic overview of the available literature on histopathological features, risk factors and results of preventive strategies on niche development to gain more insight into the underlying mechanisms. Based on current published data histopathological findings associated with niche development were necrosis, fibrosis, inflammation, adenomyosis and insufficient approximation. Patient-related risk factors included multiple CS, BMI and smoking. Labour-related factors were CS before onset of labour, extended cervical dilatation, premature rupture of membranes and presenting part of the fetus at CS below the pelvic inlet. Preventive strategies should focus on the optimal level of incision, training of surgeons and full-thickness closure of the myometrium (single or double-layer) using non-locking sutures. Conflicting data exist concerning the effect of endometrial inclusion. Future studies without heterogeneity in population, using standardized performance of the CS after proper training and using standardized niche evaluation with a relevant core outcome set are required to allow meta-analyses and to develop evidence-based preventive strategies. These studies are needed to reduce the prevalence of niches and prevent complications in subsequent pregnancies such as caesarean scar pregnancies.

Effect of single- versus double-layer uterine closure during caesarean section on postmenstrual spotting (2Close): multicentre, double-blind, randomised controlled superiority trial.

OBJECTIVE: To evaluate whether double-layer uterine closure after a first caesarean section (CS) is superior compared with single-layer uterine closure in terms of postmenstrual spotting and niche development in the uterine caesarean scar. DESIGN: Multicentre, double-blind, randomised controlled superiority trial. SETTING: Thirty-two hospitals in the Netherlands. POPULATION: A total of 2292 women aged ≥18 years undergoing a first CS were randomly assigned to each procedure (1:1): 1144 women were assigned to single-layer uterine closure and 1148 women were assigned to double-layer uterine closure. METHODS: Single-layer unlocked closure and double-layer unlocked closure, with the second layer imbricating the first. MAIN OUTCOME MEASURES: Number of days with postmenstrual spotting during one menstrual cycle 9 months after CS. SECONDARY OUTCOMES: perioperative and menstrual characteristics; transvaginal ultrasound measurements. RESULTS: A total of 774 (67.7%) women from the single-layer group and 770 (67.1%) women from the double-layer group were evaluable for the primary outcome, as a result of drop-out and amenorrhoea. The mean number of postmenstrual spotting days was 1.33 (bootstrapped 95% CI 1.12-1.54) after single-layer closure and 1.26 (bootstrapped 95% CI 1.07-1.45) after double-layer closure (adjusted mean difference -0.07, 95% CI -0.37 to 0.22, P = 0.810). The operative time was 3.9 minutes longer (95% CI 3.0-4.9 minutes, P < 0.001) and niche prevalence was 4.7% higher (95% CI 0.7-8.7%, P = 0.022) after double-layer closure. CONCLUSIONS: The superiority of double-layer closure compared with single-layer closure in terms of postmenstrual spotting after a first CS was not shown. Long-term obstetric follow-up of our trial is needed to assess whether uterine caesarean closure guidelines should be adapted. TWEETABLE ABSTRACT: Double-layer uterine closure is not superior for postmenstrual spotting after a first caesarean; single-layer closure performs slightly better on other outcomes.

Single- versus double-layer closure of the caesarean (uterine) scar in the prevention of gynaecological symptoms in relation to niche development - the 2Close study: a multicentre randomised controlled trial.

BACKGROUND: Double-layer compared to single-layer closure of the uterus after a caesarean section (CS) leads to a thicker myometrial layer at the site of the CS scar, also called residual myometrium thickness (RMT). It possibly decreases the development of a niche, which is an interruption of the myometrium at the site of the uterine scar. Thin RMT and a niche are associated with gynaecological symptoms, obstetric complications in a subsequent pregnancy and delivery and possibly with subfertility. METHODS: Women undergoing a first CS regardless of the gestational age will be asked to participate in this multicentre, double blinded randomised controlled trial (RCT). They will be randomised to single-layer closure or double-layer closure of the uterine incision. Single-layer closure (control group) is performed with a continuous running, unlocked suture, with or without endometrial saving technique. Double-layer closure (intervention group) is performed with the first layer in a continuous unlocked suture including the endometrial layer and the second layer is also continuous unlocked and imbricates the first. The primary outcome is the reported number of days with postmenstrual spotting during one menstrual cycle nine months after CS. Secondary outcomes include surgical data, ultrasound evaluation at three months, menstrual pattern, dysmenorrhea, quality of life, and sexual function at nine months. Structured transvaginal ultrasound (TVUS) evaluation is performed to assess the uterine scar and if necessary saline infusion sonohysterography (SIS) or gel instillation sonohysterography (GIS) will be added to the examination. Women and ultrasound examiners will be blinded for allocation. Reproductive outcomes at three years follow-up including fertility, mode of delivery and complications in subsequent deliveries will be studied as well. Analyses will be performed by intention to treat. 2290 women have to be randomised to show a reduction of 15% in the mean number of spotting days. Additionally, a cost-effectiveness analysis will be performed from a societal perspective. DISCUSSION: This RCT will provide insight in the outcomes of single- compared to double-layer closure technique after CS, including postmenstrual spotting and subfertility in relation to niche development measured by ultrasound. TRIAL REGISTRATION: Dutch Trial Register ( NTR5480 ). Registered 29 October 2015.

Sonographic examination of uterine niche in non-pregnant women: a modified Delphi procedure.

OBJECTIVE: To generate guidance for detailed uterine niche evaluation by ultrasonography in the non-pregnant woman, using a modified Delphi procedure amongst European experts. METHODS: Twenty gynecological experts were approached through their membership of the European Niche Taskforce. All experts were physicians with extensive experience in niche evaluation in clinical practice and/or authors of niche publications. By means of a modified Delphi procedure, relevant items for niche measurement were determined based on the results of a literature search and recommendations of a focus group of six Dutch experts. It was predetermined that at least three Delphi rounds would be performed (two online questionnaires completed by the expert panel and one group meeting). For it to be declared that consensus had been reached, a consensus rate for each item of at least 70% was predefined. RESULTS: Fifteen experts participated in the Delphi procedure. Consensus was reached for all 42 items on niche evaluation, including definitions, relevance, method of measurement and tips for visualization of the niche. A niche was defined as an indentation at the site of a Cesarean section with a depth of at least 2 mm. Basic measurements, including niche length and depth, residual and adjacent myometrial thickness in the sagittal plane, and niche width in the transverse plane, were considered to be essential. If present, branches should be reported and additional measurements should be made. The use of gel or saline contrast sonography was preferred over standard transvaginal sonography but was not considered mandatory if intrauterine fluid was present. Variation in pressure generated by the transvaginal probe can facilitate imaging, and Doppler imaging can be used to differentiate between a niche and other uterine abnormalities, but neither was considered mandatory. CONCLUSION: Consensus between niche experts was achieved regarding ultrasonographic niche evaluation. © 2018 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of the International Society of Ultrasound in Obstetrics and Gynecology.

Uterine caesarean closure techniques affect ultrasound findings and maternal outcomes: a systematic review and meta-analysis.

BACKGROUND: Caesarean section (CS) rates are rising globally. Long-term adverse outcomes after CS might be reduced when the optimal uterine closure technique becomes evident. OBJECTIVE: To determine the effect of uterine closure techniques after CS on maternal and ultrasound outcomes. SEARCH STRATEGY: Literature search in electronic databases. SELECTION CRITERIA: Randomised controlled trials (RCTs) or prospective cohort studies that evaluated uterine closure techniques and reported on ultrasound findings, perioperative or long-term outcomes. DATA COLLECTION AND ANALYSIS: Twenty studies (15 053 women) were included in our meta-analyses for various outcomes. We calculated pooled risk ratios (RR) and weighted mean differences (WMD) with 95% CI through random-effect analysis. MAIN RESULTS: Residual myometrium thickness (RMT), reported in eight studies (508 women), decreased by 1.26 mm after single- compared with double-layer closure (95% CI -1.93 to -0.58), particularly when locked sutures were used. Healing ratio [RMT/adjacent myometrium thickness (AMT)] decreased after single-layer closure (WMD -7.74%, 95% CI -13.31 to -2.17), particularly in the case of locked sutures. Niche prevalence increased (RR 1.71, 95% CI 1.11-2.62) when the decidua was excluded. Dysmenorrhea occurred more often in the single-layer group (RR 1.23, 95% CI 1.01-1.48), whereas incidence of uterine rupture was similar (RR 1.91, 95% CI 0.63-5.74). CONCLUSION: Double-layer unlocked sutures are preferable to single-layer locked sutures regarding RMT, healing ratio and dysmenorrhoea. Excluding the decidua seems to result in higher niche prevalence. As thin residual myometrium or niches may serve as intermediates for gynaecological and reproductive outcomes, future studies should focus on these outcomes. TWEETABLE ABSTRACT: #Uterineclosuretechniques after #caesarean affect #longtermoutcomes.