Over the last ten years, the prevalence of cesarean sections has risen to 21% worldwide, and by 2030, it is expected to reach 28.5% [1,2]. The rate in Pakistan rose dramatically from 2.7% in 1990 to 22.3% in 2017 [3,4]. A mix of medical and non-medical reasons, including maternal age, education, urban residency, maternal choices, financial incentives, and defensive medical practices, contribute to the trend of rise [3,5].

The formation of post-cesarean residual niches, which are critical risk factors for placenta accreta spectrum (PAS) illnesses, is influenced by the uterine closure technique used following c-section. Smaller niche dimensions and greater residual myometrial thickness have been linked to the endometrium-free closure approach, which lowers the likelihood of PAS problems [6]. Additionally, compared to a single-layer method, a double-layer uterine closure technique has shown better cesarean scar healing, leading to greater residual myometrial thickness and a decreased incidence of niche formation [7]. In comparison to single-layer closure, the parallel-layer closure technique increases residual myometrial thickness and reduces the incidence of isthmocele formation, which further improves post-operative results [8,9].

Long-term niche development effects are still being investigated, and surgeon choice and clinical circumstances are taken into consideration when choosing continuous versus interrupted sutures [10,11]. Prioritizing RMT, many surgeons prefer double-layer suturing due to its superior scar healing and lower chance of uterine rupture [12]. In high-volume settings, single-layer suturing is taken into consideration due to its shorter length; nevertheless, this advantage is balanced against the hazards of niches and possible scar healing [13].

A lower uterine segment (LUS) thickness of less than 3.6 mm greatly raises the risk of scar dehiscence and uterine rupture, making an earlier delivery and avoidance of vaginal birth after cesarean (VBAC) necessary. Uterine scar thickness is a crucial factor in determining uterine integrity [6,11]. In order to approve subsequent pregnancies, a recommended scar thickness of at least 70% of the surrounding area must be met. Post-operative examinations employing MRI and sonohysterograms can determine scar thickness and healing [8,9].

The objective of this study is to ascertain how post-cesarean residual niche formation and residual myometrial thickness (RMT) are affected by single-layer versus double-layer uterine closure and to determine how continuous versus interrupted suturing techniques affect the integrity of the uterus and the healing of cesarean scars.

The study was a retrospective comparative study, carried out in the Department of Obstetrics and Gynecology, Saidu Teaching Hospital, Swat. Data collection and analysis were conducted between September and November 2025 and the Institutional Review Board gave ethical permission on 26 August 2025. A total of 532 women who had lower-segment cesarean section (LSCS) in the hospital during the period between August 2023 and July 2025 were included in the study. All the participants were categorized into 2 equal groups (Uterine closure technique in the operative notes): Group A (single-layer, n = 266) and Group B (two-layered, n = 266). The sample size was determined with the help of the OpenEpi software with a 95% confidence interval and 80% power with reference to the previously reported incidences of 48.4% in the single-layer group and 36.5% in the double-layer group. Women between the ages of 18 and 45 years, primiparous or multiparous, and with one previous cesarean delivery and singleton term pregnancies (37 weeks or older) were eligible in case either the single-layer or the double-layer uterine closure had been recorded in their medical histories. Only the cases where postoperative transvaginal ultrasonography (TVS) or saline infusion sonohysterography (SIS) were available to them as a part of regular clinical follow-up within 6 months of surgery were considered. Unfinished and absent records, uterine malformations, intraoperative bleeding necessitating compression sutures, placenta previa or placenta accreta spectrum disorders, multiple pregnancies, past pelvic infections or endometritis, and contraindication of imaging were eliminated. Included in the structured proforma were the retrospective retrieval of data using hospital electronic databases and patient files. Demographic data of the patient, operative, suturing pattern and image evidence of the prior postoperative assessment were gathered. No further interaction or process with the patient was conducted to this end. Scar healing was measured based on the imaging reports of residual myometrial thickness (RMT) and niche presence or absence (a defect at least 2 mm deep at the scar site). Hospital records of patient-reported outcomes including menstrual changes, pelvic pain, and postnatal pregnancy complications were also examined. SPSS version 25 was used to analyze all data. The continuous variables, including age, BMI, gestational age, RMT, and niche size, were reported as the mean and standard deviation or as the median and interquartile range, based on the presence of normality and tested by the ShapiroWilk. Frequencies and percentages were used to present categorical variables such as suture technique, scar integrity, and niche presence, and pregnancy outcomes. The Chi-square test or the Fisher Exact test was used to compare groups of categorical variables and the independent t-test or the Mann–Whitney U test was used to compare groups of continuous variables. A p-value below 0.05 was taken to be statistically significant. Post-cesarean residual niche development is the defect of the cesarean scar that is 2 mm deep or more and this can be detected by transvaginal ultrasonography or saline infusion sonohysterography. The quality of healing of the cesarean scar is measured by relative myometrial thickness (RMT) that measures the amount of myometrial layer remaining at the scar site. Uterine closure procedures are highly important in scar healing; a single layer closure involves a single line of suture whereas two layers are involved in double layer closure to improve myometrial approximation. Suturing comes in two ways, the interrupted sutures that help in the distribution of the stress and the continuous sutures that use one continuous suture. The good enough RMT and minimal niche development are indications of optimal healing, which increases the integrity of the uterus as a whole and decreases the risks of scar dehiscence or rupture in future pregnancies.

The study involved 532 women who were evenly split in 266 women in each group. Group A involved single-layer uterine closure and Group B involved double-layer uterine closure. The members of the double-layer group were a bit younger with the mean age of 25.7 +/- 5.6 years versus 26.8 +/- 6.1 years in the single-layer group but the difference did not pass the statistical test. Body habitus also did not differ significantly as the mean body mass index of the single-layer group and the double-layer group were 28.3 ± 1.9 kg/m 2 and 28.2 ± 2.4 kg/m 2, respectively.

There was a considerable variation in postoperative imaging results retrieved in six months of the surgery based on the hospital records. The single layer group had more cases of post- cesarean forming niche (128 cases(48%)) than the double layer group (72 cases(27%)) (p = 0.002). The mean residual myometrial thickness (RMT) was also significantly greater in the group of two layers (5.7 ± 1.3 mm) as compared to the group of single layer (4.2 ± 1.1 mm) with highly significant p-value of 0.001. These results show that the double-layered closure could be superior in healing uterine scar and preserving more myometrial thickness.

Table 1. Type of uterine closure and its effect on niche formation and RMT.

In the comparison of the interrupted and continuous suturing methods, no meaningful difference was found to exist in the remaining myometrial thickness (RMT). Both groups had a median RMT of 11mm (inter-quartile 9-13mm) (p=0.531), which shows that the suture technique itself did not have a significant effect on the myometrial thickness at the cesarean scar site.

In terms of cesarean scar defects (CSD) 128 women (48%) in continuous group and 115 women (43) in interrupted group had scar defects which could be detected, and the difference was not significant (p = 0.539). Nonetheless, when the magnitude of defects were taken into account, there were high variations. In the continuous group only, severe CSDs were found to be associated with 64 women (24%) and only 8 women (3%) in the interrupted group (p = 0.002), indicating that continuous suturing might be linked to a high incidence of severe scar defects.

The number of times intraoperative bleeding necessitated the use of additional stitches was recorded higher in the interrupted group at 1 (range 017) as opposed to the continuous group, which had 0 (range 017) extra stitch only. This observation implies that interrupted suturing can be accompanied by the need to provide further intervention to contain bleeding.

Table 2. Sonohysterography findings within six months after cesarean section.

CSD: Cesarean section scar defect, RMT: Residual myometrial thickness.

It is a retrospective study that considered the effect of various uterine closure modalities on post-cesarean uterine healing with emphasis laid on niche development, residual myometrial thickness (RMT), and severity of cesarean scar defects (CSDs). It was found that double-layer uterine closure produced more residual myometrial thickness and a much lower rate of post-cesarean niche formation than single-layer closure. These findings are in line with some past researchers have found out that double-layer closure is the one that enhances uterine wall approximation and enhances regeneration of the anatomy [1416]. The 48 percent niche formation rate among single-layer group is consistent with the other previous studies who had used transvaginal sonography (TVS) and saline infusion sonohysterography (SIS) studies and reported the detection rate of niche after single-layer closure to be 56-64 percent [14]. Conversely, the double-layer group of the present study demonstrated significantly fewer incidences (27%), which promotes the idea that a second band of closure positively influences myometrial apposition and defect generation. The results can be compared with randomized trials that showed the lower rate of niche formation with double-layer closure (36.5%) than with single-layer closure (48.4%) [17]. Moreover, the average RMT was clearly larger in the double-layer (5.7 ± 1.3 mm) compared to single-layer (4.2 ± 1.1 mm) layer, which indicates that the thickness of the uterine wall is more preserved with the use of the double-layer closure. The significance of this parameter is in the assessment of uterine integrity especially in women who have future pregnancy plans. It has been previously documented that a less than 2.0 mm of myometrial thickness is linked to a higher risk of subsequent pregnancy uterine rupture, particularly when single-layer closure takes place [18]. In comparison, between continuous and interrupted suturing techniques, there was no significant difference in RMT (median 11 mm, IQR 9 13 mm), which shows that there is no notable difference in overall scar thickness. Nevertheless, there was a much higher rate of severe CSDs in cases of continuous suturing (24% vs. 3% in cases of interrupted suturing, p = 0.002). The observation indicates that discontinuous sutures could be more evenly distributed and help to heal the tissues. It has been suggested that too much tension on the continuous sutures can bring about localized ischemia, which will result in worse remodeling of the scar [1921] in the past. The interrupted group had more additional sutures to stop intraoperative bleeding (median of one extra stitch) than the continuous group which had none. The current observation reinforces the fact that, continuous suture is better at immediate hemostasis but perhaps at the cost of the best quality of the scar in the long term. The same has been observed in previous researches where better hemostasis was observed with continuous suture but with caution being taken as it may have negative consequences in terms of scarring [2225]. The causal interpretation of this study is limited to the retrospective design since data were gathered based on already obtained hospital records and imaging reports during the six months after surgery. Potential confounding factors including differences in surgical skill and suture material could not be fully managed. Single-centre hinders generalizability as well. Moreover, the six months follow up limited the measurement of the late reproductive outcomes like uterine rupture or placenta accreta spectrum disorders during consequent pregnancies. It is suggested that future multicenter researches with standardized imaging regimens and extended follow-ups can confirm the long-term effects of different closure methods on the integrity of the uterine scar, reproductive performance, and complications of the scar.

In comparison to single-layer closure, this study shows that double-layer uterine closure considerably lowers the incidence of post-cesarean niche development and produces a larger residual myometrial thickness (RMT), indicating better uterine scar healing and structural integrity. Continuous suturing was linked to a much higher prevalence of severe cesarean scar abnormalities, but there was no discernible difference in RMT between the two suturing methods. These results emphasize the significance of carefully choosing surgical techniques during cesarean deliveries by demonstrating the impact of uterine closure and suturing techniques on postoperative uterine healing and future reproductive outcomes.

Declarations

Conflict of interest: None

Funding: None

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