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

Normalization of subendometrial peristalsis in women with a large uterine niche following laparoscopic niche repair: A prospective cohort study

OBJECTIVE

To study the impact of laparoscopic niche repair on subendometrial peristalsis in women with a large niche.

METHODS

A explorative prospective cohort study that included women with a large niche (residual myometrium ≤ 3 mm), actual wish to conceive who were scheduled for laparoscopic niche repair. To analyse the effect of a laparoscopic niche repair on the uterine anatomy and subendometrial peristalsis, all participants underwent a 4-5 min transvaginal ultrasound before surgery and three months post-surgery during the mid-luteal phase of the menstrual cycle. Subendometrial peristalsis was evaluated by strain analysis using a dedicated two-dimensional optical flow speckle tracking method. The following features were extracted from the strain signals: frequency, amplitude, velocity, coordination and direction of coordination.

RESULTS

Post-surgery, the mean niche volume significantly decreased, with a mean reduction of 963.9 mm3 (95 % CI 382.0-1545.7). Additionally, the residual myometrium thickness increased significantly, with a mean difference of 5.8 mm (95 % CI 6.8 to 4.7). Of the subendometrial peristalsis, a significant improvement of the frequency was observed. Although amplitude, velocity, and direction of the contractions shifted towards normal values, these changes did not reach statistical significance in this pilot study. The improvements in individual peristaltic characteristics were closely associated with reductions in niche volume and enlargement of residual myometrium.

CONCLUSION

Subendometrial peristalsis is disturbed in women with a large niche. Individual contraction parameters such as velocity, amplitude and frequency decreased following laparoscopic niche repair which might be favourable for fertility purposes. These changes were associated with a reduction in niche volume and enlargement of the residual myometrium and warrant further validation in a larger cohort study.

Ultrasound outcomes and surgical parameters of the double-layer purse-string uterine closure technique in cesarean delivery: a systematic review and meta-analysis of randomized trials

BACKGROUND

A cesarean scar defect is a structural abnormality in the myometrium at the site of a prior cesarean incision, primarily influenced by the closure technique. Purse-string uterine suturing (PSUS) may reduce the incidence of cesarean scar defects and improve uterine integrity. However, the literature presents inconsistent findings, necessitating a systematic evaluation. This systematic review and meta-analysis of randomized controlled trials (RCTs) aims to assess the impact of PSUS on ultrasound outcomes and surgical parameters related to cesarean scars.

METHODS

This systematic review and meta-analysis involved a search for relevant publications in English and Persian across multiple databases, including PubMed, the Cochrane Library, Google Scholar, Scopus, Web of Science, and SID. The search was unrestricted by date and included all available publications up to August 8, 2024. The risk of bias in the included studies was evaluated using the Risk of Bias 2 (ROB2) tool, while the certainty of the evidence was assessed through the GRADE approach. Meta-regression was employed to investigate potential risk factors for cesarean scar defects, and trial sequential analysis was conducted to mitigate Type I and Type II errors.

RESULTS

A total of 353 studies were identified through the search strategy, with 8 studies included in the analysis. The meta-analysis demonstrated a significant reduction in the rate of cesarean scar defects in the PSUS group compared to the control group (risk ratio [RR] 0.45, 95% confidence interval [CI] 0.36 to 0.58; 8 trials, 751 participants, I² = 0%, indicating no heterogeneity). Additionally, a shorter uterine incision length was observed in the PSUS group compared to the control group (MD -3.84, 95% CI -4.97 to -2.71; 4 trials, 438 participants, I² = 80%, suggesting substantial heterogeneity). The PSUS group also exhibited greater residual myometrium thickness (RMT) than the control group (MD 1.33, 95% CI 0.72 to 1.94; 5 trials, 417 participants, I² = 92%, indicating considerable heterogeneity). However, no statistically significant differences were found between the PSUS and control groups regarding operation time (p = 0.10, I² = 67%, suggesting moderate heterogeneity), length (p = 0.14, I² = 98%, indicating considerable heterogeneity), height (p = 0.10, I² = 76%, suggesting substantial heterogeneity) of incision defects, or blood loss during the procedure (p = 0.94, I² = 0%, indicating no heterogeneity).

CONCLUSIONS

The use of PSUS during cesarean sections significantly reduces the occurrence of cesarean scar defects, indicating a clear clinical benefit with moderate certainty. However, the evidence for other ultrasound evaluation outcomes and surgical parameters remains of low to very low certainty. Therefore, further research is essential to validate these findings and assess the long-term clinical implications of integrating PSUS into cesarean procedures.

Reevaluating the variation of cesarean scar defect

AIM

The increasing incidence of cesarean sections has led to a higher prevalence of cesarean scar defects (CSDs), predominantly characterized by postmenstrual bleeding in affected women. CSD manifests in various forms, including isolated myometrial defects, intrauterine cystic protrusions, and extrauterine cystic extensions. The pathophysiological mechanisms underpinning CSD and its associated symptoms remain insufficiently understood. This review explores the pathogenesis of CSD, highlights its morphological characteristics with an emphasis on variable clinical diversity, and addresses the challenges for future research.

METHODS

A comprehensive narrative review was conducted using electronic databases, including PubMed and Google Scholar, to identify 41 relevant literatures published up to December 31, 2023.

RESULTS

The myometrium comprises two distinct layers-the inner and outer myometrium-with differences in their origin, structure, and function. Disruptions within these layers contribute to CSD development. Histopathologically, symptomatic CSD may be linked to uterine scar endometriosis, cystic adenomyosis, or endometrial cysts, suggesting that CSD, particularly those necessitating surgical intervention, are not limited to myometrial defects but may also involve iatrogenic endometriosis or adenomyosis, thereby exacerbating clinical symptoms.

CONCLUSION

This review provides an updated understanding of the histopathological features and classification of CSD, with an emphasis on elucidating its underlying pathogenesis.

Cesarean scar dehiscence in early puerperium and influence of barbed suture: tridimensional ultrasound evaluation in a randomized clinical study

PURPOSE

This study investigated the hypothesis of early dehiscence of hysterorrhaphy as the initial stage of post-cesarean uterine scar defects, examining the possible influence of barbed suture in this process.

METHODS

This longitudinal, prospective, double-blind study included 54 pregnant women with no history of cesarean section, randomized into two suture groups: #0 polyglactin or #1 barbed PDS threads. Sutures were continuous, unlocked, involved the entire myometrium in a single layer, and included the endometrium. Tridimensional transvaginal ultrasonography was performed on the second day postpartum to investigate scar dehiscence and measure its maximal width.

RESULTS

The groups had 29 and 25 participants, respectively. Ages: 18-37 (mean 25.80 ± standard error of the mean 0.69) years old. Groups were homogeneous for labor duration, cervical thickness, edge-to-os distance, retroversion, amniotic sac rupture, and additional hemostatic sutures required. Uterine retroversion accounted for 7.4% of cases. Dehiscence was observed in 68.5% (3.98 ± 0.57 mm). The only factor correlating (positively) with dehiscence width was myometrial thickness, whether proximal or distal.

CONCLUSIONS

Suture type had no influence on early dehiscence, which occurred at the same rate as published niche formation rates. Tridimensional ultrasound proved effective for evaluating dehiscence.

Single-layer vs double-layer uterine closure during cesarean delivery: 3-year follow-up of a randomized controlled trial (2Close study)

BACKGROUND

The rising rate of cesarean deliveries has led to an increased incidence of long long-term complications, including niche formation in the uterine scar. Niche development is associated with various gynecologic complaints and complications in subsequent pregnancies, such as uterine rupture and placenta accreta spectrum disorders. Although uterine closure technique is considered a potential risk factor for niche development, consensus on the optimal technique remains elusive.

OBJECTIVE

We aimed to evaluate the effect of single-layer vs double-layer closure of the uterine incision on live birth rate at a 3-year follow-up with secondary objectives focusing on gynecologic, fertility, and obstetrical outcomes at the same follow-up.

STUDY DESIGN

A multicenter, double-blind, randomized controlled trial was performed at 32 hospitals in the Netherlands. Women ≥18 years old undergoing a first cesarean delivery were randomly assigned (1:1) to receive either single-layer or double-layer closure of the uterine incision. The primary outcome of the long-term follow-up was the live birth rate; with secondary outcomes, including pregnancy rate, the need for fertility treatment, mode of delivery, and obstetrical and gynecologic complications. This trial is registered on the International Clinical Trials Registry Platform www.who.int (NTR5480; trial finished).

RESULTS

Between 2016 and 2018, the 2Close study randomly assigned 2292 women, with 830 of 1144 and 818 of 1148 responding to the 3-year questionnaire in the single-layer and double-layer closure. No differences were observed in live birth rates; also there were no differences in pregnancy rate, need for fertility treatments, mode of delivery, or uterine ruptures in subsequent pregnancies. High rates of gynecologic symptoms, including spotting (30%-32%), dysmenorrhea (47%-49%), and sexual dysfunction (Female Sexual Function Index score, 23) are reported in both groups.

CONCLUSION

The study did not demonstrate the superiority of double-layer closure over single-layer closure in terms of reproductive outcomes after a first cesarean delivery. This challenges the current recommendation favoring double-layer closure, and we propose that surgeons can choose their preferred technique. Furthermore, the high risk of gynecologic symptoms after a cesarean delivery should be discussed with patients.

Isthmoceles - Accuracy of imaging diagnosis and clinical correlation with histology: A prospective cohort study

Background

Isthmoceles are a growing clinical concern.

Objectives

To evaluate the accuracy of diagnosis of isthmoceles by imaging and to correlate the dimensions with clinical symptoms and histopathology.

Materials and Methods

Prospective study of women (n=60) with ≥1 C-section undergoing hysterectomy. Isthmoceles were measured by imaging before surgery and macroscopically on the specimen after hysterectomy, followed by histological analysis.

Main outcome measures

Accuracy of isthmocele diagnosis, correlation with clinical symptoms, and histopathological findings.

Result

By imaging, isthmoceles were slightly deeper (P=0.0176) and shorter (P=0.0045) than macroscopic measurements. Differences were typically small (≤3mm). Defined as an indentation of ≥2 mm at site of C-section scar, imaging diagnosed 2 isthmoceles consequently not seen by histology and missed 3. Number of prior C-sections increased isthmocele severity but neither the incidence nor the remaining myometrial thickness (RMT) did. Severity correlated positively with symptoms and histology. However, clinical use was limited. Histological analysis revealed presence of thick wall vessels in 100%, elastosis in 40%, and adenomyosis in 38%. Isthmocele lining was asynchronous with the menstrual phase in 31%.

Conclusions

Dimensions of isthmoceles by imaging were largely accurate with occasionally large differences observed. Number of C-sections did not increase isthmocele incidence, only severity. Indication for surgery remains clinical, considering dimensions and symptoms.

What is new?

Dimensions of isthmoceles should be confirmed before surgery since uterine contractions might change those dimensions. Symptoms increase with dimensions of isthmoceles but are not specific. Endometrial lining within the isthmocele can be asynchronous with the menstrual phase.

The Novel Parallel Closure Technique Compared to Single-Layer Closure of the Uterus After Primary Cesarean Section Decreases the Incidence of Isthmocele Formation and Increases Residual Myometrial Thickness

Background Isthmocele or a scar defect is a relatively common consequence of cesarean section resulting in menstrual disturbances and infertility and may compromise the myometrial integrity of the uterus in women contemplating subsequent vaginal birth. Several preventive measures have been suggested, including the modification of surgical techniques used for the closure of the uterine incision. The current study aimed to compare the incidence of isthmocele and assess residual myometrial thickness in women who underwent single versus parallel layered closure to approximate the endo-myometrial layer during cesarean section. Methodology This retrospective study evaluated data of women undergoing their first cesarean section under elective conditions (n = 497) where the uterine incision was closed using a single (n = 295) or a parallel layer (n = 202) technique. Patients were evaluated twice, at 3-6 months and 18 months postpartum, with a transvaginal ultrasound noting the presence or absence of an isthmocele and measurement of the residual myometrial thickness. Results Regardless of the closure technique, 64 (12.9%) women had an ultrasound-diagnosed isthmocele. Significantly fewer patients in the parallel-layer closure group presented with an isthmocele both at 3-6 (13.6 vs. 6.9%; p = 0.019) and 18 months (16.3 vs. 7.8%; p = 0.009) postpartum. Residual myometrium was significantly thicker in the parallel-layer closure group (8.0 vs. 13.2 mm at 3-6 months postpartum; p = 0.000 and 7.2 vs. 12.3 mm at 18 months postpartum; p = 0.004). For all patients, a retroverted position of the uterus at 3-6 months follow-up examination significantly increased the frequency of isthmocele (36/395 (9.1%) with an anteverted uterus and 18/102 (17.6%) with a retroverted uterus; p = 0.002). In patients with a single-layer closure, a retroverted uterus at the 3-6-month follow-up was associated with an isthmocele in 29.5% (18/61) of patients, while no isthmocele was recorded when the uterus was retroverted in the parallel-layer closure group (0/41) (p = 0.001). At 18 months postpartum, of the 64 patients with an isthmocele, 26 (40.6%) presented with abnormal uterine bleeding mainly in the form of postmenstrual spotting. Of the 26 patients with abnormal bleeding, 23 were in the single-layer and three were in the parallel-layer closure group. Conclusions The parallel-layer closure when compared to a single-layer closure of the uterine incision in patients undergoing primary cesarean section decreased the incidence of isthmocele formation and increased residual myometrial thickness. More patients in the single-layer closure group had menstrual cycle disturbances at 18 months postpartum.

Caesarean Section Scar and Placental Location at the First Trimester of Pregnancy-A Prospective Longitudinal Study

Background and Objectives: This study aims to report the location of the placenta in the first trimester of pregnancy in groups of women according to the number of previous caesarean deliveries and the visibility of the caesarean scar niche. Materials and Methods: The prospective observational research included adult women aged 18 to 41 years during pregnancy after one or more previous caesarean sections (CSs). Transvaginal (TVS) and transabdominal sonography (TAS) was used to examine the uterine scar and placental location during 11-14 weeks. The CS scar niche ("defect") was bordered in the sagittal plane as a notch at the previous CS scar's site with a depth of 2.0 mm or more. A comparative analysis of the placental location (high or low and anterior or posterior) was performed between groups of women according to the CS number and the CS scar niche. Results: A total of 122 participants were enrolled during the first-trimester screening. The CS scar defect ("niche") was visible in 40.2% of cases. In cases after one previous CS, the placenta was low in the uterine cavity (anterior or posterior) at 77.4%, and after two or more CSs, it was at 67.9%. Comparing the two groups according to the CS scar niche, the placenta was low in 75.5% of cases in the participant group with a CS scar niche and in 75% of cases without a CS scar niche (p = 0.949). Conclusions: The number of previous caesarean deliveries has no effect on the incidence rate of low-lying placentas in the first trimester. Moreover, the presence of the CS scar niche is not associated with anterior low-lying placentas.