Intra-cavitary fluid resulted from caesarean section but not isthmocele compromised clinical pregnancy after IVF/ICSI treatment

The impact of caesarean scar niche on fertility - a systematic review

BACKGROUND

The trend of increasing caesarean section (CS) rates brings up questions related to subfertility. Research regarding the influence of CS on assisted reproduction techniques (ART) is conflicting. A potential mechanism behind CS-induced subfertility is intra uterine fluid resulting from a caesarean scar defect or niche. The vaginal microbiome has been repeatedly connected to negative ART outcomes, but it is unknown if the microbiome is changed in relation to a niche.

METHODS

This systematic review describes literature investigating the effect of a niche on live birth rates after assisted reproduction. Furthermore, studies investigating a difference in microbial composition in subfertile persons with a niche compared to no niche are evaluated. Pubmed, Embase and Web of Science were searched on March 2023 for comparative studies on both study questions. Inclusion criteria were i.e., English language, human-only studies, availability of the full article and presence of comparative pregnancy data on a niche. The quality of the included studies and their risk of bias were assessed using the Newcastle-Ottawa scale for cohort studies. The results were graphically displayed in a forest plot.

RESULTS

Six retrospective cohort studies could be included on fertility outcomes, with a total of 1083 persons with a niche and 3987 without a niche. The overall direction of effect shows a negative impact of a niche on the live birth rate (pooled aOR 0.58, 95% CI 0.48-0.69) with low-grade evidence. Three studies comparing the microbiome between persons with and without a CS could be identified.

CONCLUSION

There is low-grade evidence to conclude that the presence of a niche reduces live birth rates when compared to persons without a niche. The theory that a caesarean has a negative impact on pregnancy outcomes because of dysbiosis promoted by the niche is interesting, but there is no sufficient literature about this.

Effect of previous caesarean section on reproductive and pregnancy outcomes after assisted reproductive technology: A systematic review and meta‑analysis

Pregnancies following previous caesarean section (CS) are associated with higher incidence of infections, postpartum haemorrhage and obstetric complications. The present study aimed to explore the effect of previous CS on reproductive, maternal and neonatal outcomes in women who underwent assisted reproductive techniques (ART). A systematic review and meta-analysis were conducted to assess reproductive and pregnancy outcomes following ART in women with and without a previous CS. Preferred Reporting Items for Systematic reviews and Meta-Analyses guidelines were followed. Eligible language articles written in English, published up to October 2023, were identified in Medline, Google Scholar and Science Direct databases. The quality of the included studies was assessed using the Newcastle Ottawa Scale. A total of 19 articles, reporting on 13 different outcomes met the inclusion criteria. It was revealed that women with previous CS had 9% lower clinical pregnancy rates, 13% lower live birth rates, 11% lower implantation rates and 28% lower multiple pregnancy rates compared with women who had prior natural vaginal deliveries. Additionally, previous CS was associated with an 8-fold higher risk of difficult embryo transfers. No significant differences were noted in ectopic pregnancy rates, miscarriage rates or biochemical pregnancy rates. The present systematic review and meta-analysis demonstrated that previous CS is associated with decreased prospects of clinical pregnancy, live birth and successful embryo implantation during ART. The findings of the present study underscored the need to counsel women with prior CS regarding its potential impact on ART outcomes.

Effect of hysteroscopic surgery on IVF/ICSI pregnancy outcomes for different cesarean scar diverticulum severity: A retrospective cohort study

OBJECTIVE

To investigate associations between hysteroscopic surgery for patients with varying cesarean scar diverticulum (CSD) severity and in vitro fertilization (IVF)/intracytoplasmic sperm injection (ICSI) embryo transfer (ET) pregnancy outcomes, focusing also on the correlation between the CSD size with its severity, and pregnancy outcomes.

METHODS

A retrospective study was conducted on patients with CSD who underwent IVF/ICSI-ET at a university-based hospital between January 2017 and July 2023. Patients were categorized into four groups based on CSD severity and whether they received hysteroscopic surgery: a mild surgical group (Group A, n = 86), a mild non-surgical group (Group B, n = 30), a moderate-to-severe surgical group (Group C, n = 173), and a moderate-to-severe non-surgical group (Group D, n = 96). Baseline characteristics and pregnancy outcomes were compared among these groups. Correlation assessments were conducted to explore relationships between CSD size with its severity, and pregnancy outcomes.

RESULTS

Compared with Group D, Group C exhibited significantly increased rates of biochemical pregnancy (odds ratio [OR] 1.90; 95% confidence interval [CI] 1.03-3.51, P = 0.041), clinical pregnancy (OR 2.30; 95% CI1.18-4.45; P = 0.014), and live birth (OR 2.77; 95% CI 1.10-7.00, P = 0.031). However, no differences in pregnancy outcomes were observed between Groups A and B. Correlation analyses revealed significant positive associations between CSD severity and its depth, length, width, and volume.

CONCLUSIONS

Patients with moderate-to-severe CSD achieved favorable IVF/ICSI pregnancy outcomes following hysteroscopic surgery. The CSD size was significantly related to its severity.

Fungal-bacteria interactions provide shelter for bacteria in Caesarean section scar diverticulum

Caesarean section scar diverticulum (CSD) is a significant cause of infertility among women who have previously had a Caesarean section, primarily due to persistent inflammatory exudation associated with this condition. Even though abnormal bacterial composition is identified as a critical factor leading to this chronic inflammation, clinical data suggest that a long-term cure is often unattainable with antibiotic treatment alone. In our study, we employed metagenomic analysis and mass spectrometry techniques to investigate the fungal composition in CSD and its interaction with bacteria. We discovered that local fungal abnormalities in CSD can disrupt the stability of the bacterial population and the entire microbial community by altering bacterial abundance via specific metabolites. For instance, Lachnellula suecica reduces the abundance of several Lactobacillus spp., such as Lactobacillus jensenii, by diminishing the production of metabolites like Goyaglycoside A and Janthitrem E. Concurrently, Clavispora lusitaniae and Ophiocordyceps australis can synergistically impact the abundance of Lactobacillus spp. by modulating metabolite abundance. Our findings underscore that abnormal fungal composition and activity are key drivers of local bacterial dysbiosis in CSD.

Isthmocele and Infertility

Isthmocele is a gynecological condition characterized by a disruption in the uterine scar, often associated with prior cesarean sections. This anatomical anomaly can be attributed to inadequate or insufficient healing of the uterine wall following a cesarean incision. It appears that isthmocele may impact a woman's quality of life as well as her reproductive capacity. The incidence of isthmocele can range from 20% to 70% in women who have undergone a cesarean section. This review aims to sum up the current knowledge about the effect of isthmocele on fertility and the possible therapeutic strategies to achieve pregnancy. However, currently, there is not sufficiently robust evidence to indicate the need for surgical correction in all asymptomatic patients seeking fertility. In cases where surgical correction of isthmocele is deemed necessary, it is advisable to evaluate residual myometrial thickness (RMT). For patients with RMT >2.5-3 mm, hysteroscopy appears to be the technique of choice. In cases where the residual tissue is lower, recourse to laparotomic, laparoscopic, or vaginal approaches is warranted.

Effect of prior cesarean delivery on the outcomes of intracytoplasmic sperm injection

OBJECTIVE

This study was conducted to investigate the impact of previous delivery mode on pregnancy outcomes in patients with secondary infertility after frozen-thawed embryo transfer.

METHODS

This prospective observational study included 140 patients experiencing secondary infertility. Of these, 70 patients had a previous cesarean delivery (CD), while the remaining 70 patients had a previous normal vaginal delivery (NVD). The primary outcome was the implantation rate. The secondary outcomes included rates of clinical pregnancy, chemical pregnancy, miscarriage, and ectopic pregnancy.

RESULTS

The comparison of all fertility outcomes between the two groups revealed no statistically significant differences. The implantation rate was 40.4% in the CD group and 41.7% in the NVD group (p=0.842). The clinical pregnancy rate was 50% in the CD group and 49.3% in the NVD group (p=0.932), while the chemical pregnancy rate was 14.6% in the CD group and 19% in the NVD group (p=0.591). The miscarriage rates in the CD and NVD groups were 20% and 17.6%, respectively (p=0.803). One case of tubal ectopic pregnancy occurred in the NVD group (1.4%).

CONCLUSION

The mode of prior delivery did not significantly impact pregnancy outcomes following frozen-thawed embryo transfer.

Isthmocele, not cesarean section per se, reduces in vitro fertilization success: a systematic review and meta-analysis of over 10,000 embryo transfer cycles

IMPORTANCE

Previous reviews have shown that a history of cesarean section (CS) is associated with a worse in vitro fertilization (IVF) prognosis. To date, whether the decline in the IVF chances of success should be attributed to the CS procedure itself or to the presence of isthmocele remains to be clarified.

OBJECTIVE

To summarize the available evidence regarding the impact of isthmocele on IVF outcomes.

DATA SOURCES

Electronic databases and clinical registers were searched until May 30, 2023.

STUDY SELECTION AND SYNTHESIS

Observational studies were included if they assessed the effect of isthmocele on IVF outcomes. Comparators were women with isthmocele and women without isthmocele with a previous CS or vaginal delivery. Study quality was assessed using the modified Newcastle-Ottawa Scale.

MAIN OUTCOMES

The primary outcome was the live birth rate (LBR). The effect measures were expressed as adjusted odds ratios (aORs) and unadjusted odds ratios (uORs) with 95% confidence intervals (95% CIs). The body of evidence was assessed using the Grading of Recommendations Assessment, Development and Evaluation working group methodology.

RESULTS

Eight studies (n = 10,873 patients) were included in the analysis. Women with isthmocele showed a lower LBR than both women with a previous CS without isthmocele (aOR, 0.62; 95% CI, 0.53-0.72) and those with a history of vaginal delivery (aOR, 0.55; 95% CI, 0.42-0.71). The LBRs in women with a previous CS without isthmocele and those with a history of vaginal delivery were similar (aOR, 0.74; 95% CI, 0.47-1.15). Subgroup analysis suggested a negative effect of the intracavitary fluid (ICF) in women with isthmocele on the LBR (uOR, 0.36; 95% CI, 0.18-0.75), whereas the LBRs in women without ICF and those without isthmocele were similar (uOR, 0.94; 95% CI, 0.61-1.45).

CONCLUSION AND RELEVANCE

We found moderate quality of evidence (Grading of Recommendations Assessment, Development and Evaluation grade 3/4) supporting a negative impact of isthmocele, but not of CS per se, on the LBR in women undergoing IVF. The adverse effect of isthmocele on IVF outcomes appears to be worsened by ICF accumulation before embryo transfer.

CLINICAL TRIAL REGISTRATION NUMBER

CRD42023418266.

Comparison of clinical effectiveness and subsequent fertility between hysteroscopic resection and vaginal repair in patients with cesarean scar defect: a prospective observational study

OBJECTIVE

To evaluate the clinical effectiveness and pregnancy rate after hysteroscopic resection (HR) and/or vaginal repair (VR) in patients with cesarean scar defect (CSD).

METHODS

This prospective observational study enrolled 191 patients who received CSD surgery in the First affiliated hospital of Sun Yat-sen University between September 2019 to February 2022 (96 in HR and 95 in VR, respectively). Patient follow-up were performed three months after surgery in both groups by transvaginal ultrasound to confirm the presence of fluid in the niche, along with the resolution of prolonged menses at the same time. The primary outcome was the clinical effectiveness between HR and VR, identified by the resolution of prolonged menses.

RESULTS

The rates of niche-fluid disappearance (70.1% vs 60.2%, P = 0.176) and prolonged menses resolution (74.8% vs 80.0%, P = 0.341) were comparable for HR and VR. A subgroup analysis for niche size revealed that HR provides patients with small niche a more favorable rate of menstrual resolution compared to VR (size of niche ≤ 15 mm2, aOR = 3.423, 95% confidence interval [CI] 1.073-10.918), but patients with large niche experience a lower rate of resolution compared to VR (size of niche > 25 mm2, aOR = 0.286, 95% CI 0.087- 0.938). During follow-up, 41 patients who wanted to conceive became pregnant. Kaplan-Meier estimates of the cumulative probability of pregnancy at 12 months and 24 months were 47.1% (95% CI: 34.5%, 58.8%) and 63.8% (95% CI: 52.5%, 72.9%), respectively. The median pregnancy time was 22 months (95% CI: 14.2, 29.8) after VR and 12 months (95% CI: 8.3, 15.7, Gehan-Breslow-Wilcoxon P = 0.021) after HR. Among patients with subsequent infertility, 31.6% achieved pregnancy by unassisted mode and 29.8% by IVF/ICSI. Moreover, among patients with previously failed IVF/ICSI treatment, 60% (12/20) obtained pregnancy, including 71.4% (10/14) after HR and 33.3% (2/6) after VR.

CONCLUSIONS

Hysteroscopic resection is as effective as vaginal repair at relieving symptoms of CSD-associated prolonged menses. Hysteroscopic resection is the modality of choice with an improvement in prolonged menses for small niche, while vaginal might be considered for a large niche. Furthermore, surgical intervention could improve the clinical pregnancy rate of CSD patients. All of these provide evidence for the individualized management of CSD.

Prevalence and clinical effect of caesarean scar defects in women undergoing IVF

RESEARCH QUESTION

How common are caesarean scar defects (isthmocele) among patients who have had previous caesarean delivery undergoing IVF for secondary infertility? Does the presence of isthmocele affect the chances of success of IVF?

DESIGN

In this cohort study, women referred to an Italian public assisted reproduction centre between January 2016 and April 2021 were retrospectively reviewed. Women with a history of caesarean delivery and an indication for IVF were selected. On the basis of the local policy, all patients with a history of caesarean section underwent saline contrast sonography (SCS). Sonographic evaluation was standardized.

RESULTS

One hundred and forty-four women were eligible, of whom 22 declined SCS and eight decided to delay pregnancy seeking. Overall, 114 women were available for data analysis. Seventy-six women were diagnosed with caesarean scar defects, corresponding to a prevalence of 67% (95% CI 58 to 75%). Baseline characteristics of women with and without isthmocele were similar. Conversely, the clinical pregnancy rate (adjusted OR 0.31, 95% CI 0.13 to 0.72) and live birth rate (adjusted OR 038, 95% CI 0.17 to 0.86) were significantly lower among affected women. No associations between specific sonographic defect characteristics and IVF outcome could be identified.

CONCLUSIONS

Caesarean scar defects are common among women with a history of caesarean section requiring IVF. The presence of these lesions may reduce the chance of success of the procedure.

Chronic poor healing wounds of post cesarean scar diverticulum: Altered angiogenesis and immunobiology

Cesarean section (CS) scar diverticula (CSD) is an important cause impede further fecundity, with rather complicated pathophysiologic mechanisms and unclear etiopathogenesis. In this study, we detect the influences of CSD on the pregnancy outcomes in in-vitro fertilization (IVF) or intra-cytoplasmic sperm injection (ICSI) embryo transfer (ET) cycles, and further explore the mechanisms involved based on histopathology and immunology differences in endometrium between CSD and vaginal birth (VB) women. The CS group had significantly lower CLBR compared to NCS group. Histopathological analysis showed that the higher prevalent of CE is accompanied by excessive fibroblast proliferation at the lower segment of uterus and significantly exaggerated vascular proliferation in situ. Intrauterine inflammatory cytokines including IL-1α, IL-1β, IL-6, IL-8, TNF-α and SDF-1α were also increased in CSD group. The present data suggests impaired fecundity in CSD women undergoing IVF/ICSI treatment. Although the causal relationship is ambiguous, the potential mechanisms may involve persistent inflammatory response in the uterine cavity, active vascular proliferation accompanied with increased fibrosis which are responsible for poor chronic wound healing of CSD.

Interaction between Cervical Microbiota and Host Gene Regulation in Caesarean Section Scar Diverticulum

Cesarean section scar diverticulum (CSD) has become a formidable obstacle preventing women receiving CS from reproducing. However, the pathogenesis of CSD remains unexplored. In this study, we characterized the cervical microbiota, metabolome, and endometrial transcriptome of women with CSD. Based on the 16s rRNA results of cervical microbes, the microbial diversity in the CSD group was higher than that in the control group. Lactobacillus were significantly decreased in the CSD group and were mutually exclusive with potentially harmful species (Sphingomonas, Sediminbacterium, and Ralstonia) abnormally elevated in CSD. The microbiota in the CSD group exhibited low activity in carbohydrate metabolism and high activity in fatty acid metabolism, as confirmed by the metabolomic data. The metabolomic characterization identified 6,130 metabolites, of which 34 were significantly different between the two groups. In the CSD group, N-(3-hydroxy-eicosanoid)-homoserine lactone and Ternatin were significantly increased, in addition to the marked decrease in fatty acids due to high consumption. N-(3-hydroxy-eicosanoyl)-homoserine lactone is a regulator that promotes abnormal apoptosis in a variety of cells, including epithelial cells and vascular endothelial cells. This abnormal apoptosis of endometrial epithelial cells and neovascularization was also reflected in the transcriptome of the endometrium surrounding the CSD. In the endometrial transcriptome data, the upregulated genes in the CSD group were active in negatively regulating the proliferation of blood vessel endothelial cells, endothelial cells, and epithelial cells. This alteration in the host's endometrium is most likely influenced by the abnormal microbiota, which appears to be confirmed in the results by integrating host transcriptome and microbiome data. For the first time, this study described the abnormal activity characteristics of microbiota and the mechanism of host-microbiota interaction in CSD. IMPORTANCE Cesarean section scar diverticulum (CSD) has become a formidable obstacle preventing women receiving CS from reproducing. In this study, we revealed that potentially harmful microbes do have adverse effects on the host endometrium. The mechanism of these adverse effects includes the inhibition of the activity of beneficial bacteria such as lactobacilli, consumption of protective metabolites of the endometrium, and also the production of harmful metabolites. In the present study, we elucidated the mechanism from the perspectives of microbial, metabolic, and host responses, providing an important rationale to design preventive and therapeutic strategies for CSD.