Impact of previous Caesarean section on reproductive outcomes after assisted reproductive technology: systematic review and meta-analyses

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.

The relationship between cesarean delivery and fecundability: a population-based cohort study

BACKGROUND

Previous studies have found that women who undergo cesarean delivery have fewer pregnancies. Cesarean delivery is also more common among women with lower fecundability. The potential role of cesarean delivery in reduced fecundability is not known.

OBJECTIVE

This study aimed to assess the bidirectional relationship between cesarean delivery and fecundability.

STUDY DESIGN

This was a prospective cohort study based on data from the Norwegian Mother, Father, and Child Cohort study linked with the Medical Birth Registry of Norway. We estimated the fecundability ratio (per cycle probability of pregnancy) and relative risk of infertility (time to pregnancy ≥12 months) by mode of delivery in the previous delivery among 42,379 women. For the reverse association, we estimated the relative risk of having a cesarean delivery by fecundability (the number of cycles women needed to conceive) among 74,024 women.

RESULTS

The proportion of women with infertility was 7.3% (2707/37,226) among women with a previous vaginal delivery and 9.9% (508/5153) among women with a previous cesarean delivery, yielding an adjusted relative risk of 1.21 (95% confidence interval, 1.10-1.33). Women with a previous cesarean delivery also had a lower fecundability ratio (0.90; 95% confidence interval, 0.88-0.93) than women with a previous vaginal delivery. When assessing the reverse association between fecundability and cesarean delivery, we found that women who did not conceive within 12 or more cycles had a higher risk for cesarean delivery (adjusted relative risk, 1.57; 95% confidence interval, 1.48-1.66) than women who conceived within the first 2 cycles. The associations remained after controlling for sociodemographic and clinical risk factors and were observed across parity groups.

CONCLUSION

Among women with more than 1 child, those who had a previous cesarean delivery subsequently had a lower fecundability ratio and an increased infertility risk than those who had a vaginal delivery. However, women who needed a longer time to conceive were also more prone to be delivered by cesarean delivery, indicating a bidirectional relationship between cesarean delivery and fecundability. This could suggest a common underlying explanatory mechanism and that the surgical procedure itself may not or only partly directly influence fecundability.

Impact of cesarean scar defect on reproductive outcomes after assisted reproductive technology

In last twenty years, the cesarean section rate has been rising in China, leading to an increased prevalence of cesarean scar defect (CSD) and secondary infertility. CSD decreases receptivity of endometrium, induces adenomyosis and endometriosis, disrupts uterine micro-environment, causes difficulty of embryo transplant operation and further pregnancy complications. For women undergoing assisted reproductive technology (ART), CSD significantly reduces embryo implantation rate, clinical pregnancy rate and live birth rate. CSD can be effectively treated by hysteroscopic surgery, laparoscopic surgery and transvaginal surgery to increase the pregnancy rate. This article reviews the research progress on the impact of CSD on the reproductive outcomes of ART, the potential factors and related treatment, to provide reference for CSD management in ART patients.

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.

Impact of Caesarean section on pregnancy outcomes in ART after transfer of one or more frozen blastocysts

INTRODUCTION

The prevalence of Caesarean delivery is rising steadily worldwide, and it is important to identify its future impact on fertility. A number of articles have been published on this subject, but the impact of Caesarean section on reproductive outcomes is still under debate, and none of these articles focus exclusively on frozen blastocysts.

OBJECTIVE

The aim of this study was to evaluate the impact of a previous Caesarean delivery compared with a previous vaginal delivery on the chances of a live birth following the transfer of one or more frozen embryos at the blastocyst stage.

METHODS

This was a retrospective, bicentric study at the University Hospitals of Nîmes and Montpellier, conducted between January 1st, 2016 and February 1st, 2021. Three hundred and ninety women with a history of childbirth and a transfer of one or more frozen embryos at blastocyst stage were included in the analysis. The primary outcome was the number of live births. Secondary outcomes were: the rate of positive HCG, miscarriage, ectopic pregnancy and clinical pregnancy, as well as the live birth rate according to the presence or absence of an isthmocele.

RESULTS

Of the 390 patients included, 118 had a previous Caesarean delivery and 272 a vaginal delivery. No statistically significant differences were found for the primary (p = 0.9) or secondary outcomes. A trend towards lower live birth rates was observed in patients with isthmoceles, but this did not reach significance (p>0.9). On the other hand, transfers were more often described as difficult in the Caesarean delivery group (p = 0.011).

CONCLUSION

Our study found no effect of previous Caesarean delivery on the chances of live birth after transferring one or more frozen blastocysts. However, further prospective studies are needed to confirm these results.

Previous caesarean delivery and the presence of caesarean scar defects could affect pregnancy outcomes after in vitro fertilization frozen-thawed embryo transfer: a retrospective cohort study

BACKGROUND

Due to various iatrogenic and social factors, the global caesarean delivery (CD) rate has risen sharply in the past 30 years. It is more complicated and dangerous for women with a scarred uterus to experience pregnancy again than for women with a previous vaginal delivery (VD). In this study we investigated the impact of previous caesarean delivery (CD) and caesarean scar defects (CSDs) on pregnancy outcomes after in vitro fertilization frozen-thawed embryo transfer (IVF-FET).

METHODS

We conducted a retrospective cohort study that included 1122 women aged < 40 years who had a history of only one parturition (after 28 weeks of pregnancy) and who underwent their first FET cycle between January 2014 and January 2020. Patients were divided into the CD group, VD group, and CSD group. Thereafter, according to the number of transferred embryos, the CD, VD, and CSD groups were divided into the single embryo transfer (SET) group and the double embryo transfer (DET) group. Outcome measures in this study were live birth, clinical pregnancy, multiple pregnancy, ectopic pregnancy, pregnancy loss, pregnancy complications, preterm birth, and neonatal birth weight. Multivariate logistic regression was performed to evaluate the relationship between pregnancy outcomes and CD.

RESULTS

In SET patients, the clinical pregnancy and live birth rates were decreased in the CSD group compared with the VD and CD groups. In DET patients, the clinical pregnancy and live birth rates were significantly lower in theCSD group than in the CD and VD groups. After adjustment for confounders, previous CD and CSD were associated with a significantly lower clinical pregnancy rate and live birth rate than previous VD in the total sample. This effect was observed in DET patients, but not in SET patients. Additionally, DET patients with previous CD had a significantly higher multiple pregnancy rate (AOR = 0.47, 95% CI = 0.29, 0.75, P = 0.002) than those with previous VD, but no significant associations were observed in CSD and multiple pregnancies (AOR = 0.55, 95% CI = 0.23, 1.34, P = 0.192) between DET patients with CD and those with VD after adjusting for potential confounders.

CONCLUSIONS

Our study showed that during an FET cycle, previous CD and the presence of a CSD could negatively affect pregnancy outcomes especially in DET patients.

Influence of Maternal Age on the Relationship Between Endometrial Thickness and Ongoing Pregnancy Rates in Frozen-Thawed Embryo Transfer Cycles: A Retrospective Analysis of 2,562 Cycles

Background

In frozen-thawed embryo transfer (FET) cycles, endometrial thickness (EMT) has been used routinely as the main clinical monitoring index. However, the current findings are conflicting.

Method

This was a single-center retrospective study of 2,054 couples (2,562 cycles) who underwent FET (including cleavage stage embryos and blastocysts) between January 2017 and August 2020 in the reproductive centers of First Affiliated Hospital of Xinjiang Medical University. The primary outcome measure was the ongoing pregnancy rate (OPR); the secondary outcome was the clinical pregnancy rate.

Results

After stratified analysis and adjusting for confounders such as maternal age, duration of infertility, number of high-quality embryos transferred, endometrial preparation protocol, number of transfer cycles, and stages of embryo transferred, we found a curvilinear relationship between EMT and the OPR in women < 35 years of age. For women with EMT ≤ 8 mm, the OPR increased by 150% for cleavage stage embryo transfer for every 1 mm increase in the EMT; similarly, it increased by 97% for blastocyst stage FET. However, there was a linear relationship between EMT and OPR in women aged ≥ 35 years. When blastocysts were transferred, for every 1 mm increase in the EMT the OPR increased significantly by 12%. But OPR after frozen-thawed cleavage stage embryos transfer did not increase significantly with increased EMT.

Conclusions

Our study showed that the OPR increased significantly with increased EMT between young women aged < 35 years with EMT ≤ 8 mm and older women who underwent transfer of blastocysts.