A 2026 study found that patients with a previous cesarean delivery had slightly lower live birth rates after IVF compared to those with a previous vaginal delivery, though the reason for this difference isn’t clear.
Cesarean delivery rates have increased over the past few decades, especially among IVF patients. Because cesarean delivery involves surgery on the uterus, it’s been suggested that it could affect future implantation or pregnancy outcomes.
Possible mechanisms include scar formation, altered uterine contractility or blood flow, chronic inflammation, and the development of cesarean scar defects that could accumulate fluid and interfere with implantation.
Some studies suggest lower live birth rates after IVF in patients with a previous cesarean, while others show no difference.
Létourneau et al. (2026) conducted a large population-based study comparing embryo transfer outcomes in patients with a previous cesarean vs. vaginal delivery.
🔗 Original studies are referenced in this post or within the linked Remembryo posts.
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Study Details
- Study type: Retrospective study using linked registry data from birth and IVF databases in Ontario, Canada (2013–2020)
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Participants: 7460 patients (<42 years old) who had their first embryo transfer after a previous delivery (even if they had IVF cycles before that delivery):
- Previous vaginal delivery: 4587
- Previous cesarean delivery: 2873
- Baseline characteristics: Mostly similar between groups
- Embryos transferred: Mostly frozen single blastocyst transfers
- Primary outcome: Live birth rate after the first embryo transfer following the previous delivery
- Power calculation: Designed to detect a 5% absolute difference in live birth rate
- Statistical adjustment: Adjusted for key factors such as age, number of embryos transferred, embryo stage, and transfer type
Lower live birth rates after previous cesarean delivery
Patients with a previous cesarean had lower live birth rates compared to those with a previous vaginal delivery (32.7% vs 37.3%; adjusted risk ratio [95% CI]: 0.84 [0.80-0.90]).
There were also decreases in rates for clinical pregnancy (42.2% vs 45.8%, aRR 0.90 [0.85-0.95]), ongoing pregnancy, implantation and positive beta hCG.
When they looked at subgroups, live birth rates were lower after previous cesarean delivery in both fresh and frozen transfers, in patients under 40, and in both labor and no-labor cesareans. This difference was not seen in patients aged 40–42, likely due to smaller sample size.
Conclusion
This study found that a previous cesarean delivery was linked to a small but consistent drop in live birth rates after embryo transfer.
The authors, and other studies, suggest a few possible explanations:
- Cesarean scar defects that can trap fluid and interfere with implantation
- Chronic inflammation in the uterus
- Changes in uterine contractions or blood flow
- Structural changes to the uterine cavity
However, none of these were directly measured in this study.
It’s possible that conditions like endometriosis or adenomyosis could increase the chance of needing a cesarean and lower live birth rates on their own, but this information wasn’t available in the registry. In addition, factors like embryo quality, BMI, and surgical history were also not available and could affect live birth rates.
Overall, this is one of the stronger studies on this topic and supports a link, but it still doesn’t explain why it happens.
Want to read more about uterine factors that could affect embryo implantation?
A 2026 study found that if endometrial fluid cleared before embryo transfer, live birth rates were similar to patients without fluid. When the fluid remained, live birth rates were lower, and cancelling the cycle didn't appear to improve outcomes in a later transfer. Read more.
A 2025 study found that PCX, a surface molecule on endometrial cells, may lead to a shorter implantation window in women with endometriosis and might explain the stickiness of lesions outside the uterus. Read more.
A new study reviewed how fibroids can compromise the endometrium and prevent embryo implantation, identifying key issues such as disrupted blood flow and vascular changes, abnormal endometrial peristalsis, inflammatory responses, and changes in the microbiome. Read more.
Reference
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About Embryoman
Embryoman (Sean Lauber) is a former embryologist and the founder of Remembryo, an IVF research and fertility education website. After working in an IVF lab in the US, he returned to Canada and now focuses on making fertility research more accessible. He holds a Master’s in Immunology and launched Remembryo in 2018 to help patients and professionals make sense of IVF research. Sean shares weekly study updates on Facebook, Instagram, and Reddit regularly. He also answers questions on Reddit or in his private Facebook group.