Written by Aisha Saleem, Pharmacist & Health Writer at PharmaHealths.com
Last Updated: August 8, 2026
If your period seems to end and then a week later you are still seeing brown spotting, and you have had a c-section in the past, there is a specific and well documented explanation for this. If your period ends but brown spotting continues days later after a c-section, there may be an underlying medical reason behind it. It is called an isthmocele, and far too few women are told it might be the reason behind bleeding, pain, or even difficulty getting pregnant again.
WHAT IS AN ISTHMOCELE?
An isthmocele, also called a cesarean scar defect or uterine niche, is a small pouch that forms at the site of a previous c-section incision when the uterine muscle does not heal completely flush. Instead of healing into a smooth, even scar, a gap or indentation remains in the uterine wall. A 2025 prospective cohort study from Arash Women’s Hospital defines it clinically as a myometrial defect at least 2mm deep, detected on transvaginal ultrasound.
HOW COMMON IS ISTHMOCELE AFTER A C-SECTION?
It is far more common than most women realize. Studies using standard transvaginal ultrasound find some degree of defect in 24% to 70% of women after a c-section, and that number rises to 56% to 84% when a more sensitive scan called saline infusion sonohysterography is used. Not every defect causes symptoms, but a significant proportion of women with a defect may develop noticeable symptoms over time.
WHAT DOES POSTMENSTRUAL SPOTTING FROM AN ISTHMOCELE LOOK LIKE?
The hallmark symptom is old, brown looking blood that continues for more than two days after your period has otherwise ended, sometimes described by women as a lingering “tail” to their cycle. This happens because menstrual blood pools inside the niche itself and then drains out slowly over the following days, rather than leaving the uterus during the normal window of your period.
COMMON SYMPTOMS OF ISTHMOCELE
• Brown spotting after your period ends
• Bleeding between periods
• Pelvic pain or a feeling of heaviness
• Pain during intercourse
• Difficulty getting pregnant after a previous birth
HOW IS ISTHMOCELE DIAGNOSED?
A transvaginal ultrasound is the first and most common way to identify an isthmocele, and it will typically appear as a triangular or hypoechoic indentation at the site of your c-section scar. If the ultrasound is inconclusive but your symptoms strongly suggest a niche, your doctor may recommend a saline infusion sonohysterography, which fills the uterus with fluid to get a clearer picture of the defect’s size and depth.
CAN ISTHMOCELE CAUSE INFERTILITY?
Yes, it is a recognized cause of secondary infertility, meaning difficulty conceiving after a previous successful pregnancy. Research places the infertility risk associated with isthmocele between 4% and 19%, thought to result from blood and fluid pooling in the niche, ongoing local inflammation, and in some cases physical obstruction that interferes with embryo implantation or sperm movement through the uterus.
IS ISTHMOCELE DANGEROUS?
For most women it causes uncomfortable but not dangerous symptoms like spotting, pelvic pain, or pain during sex. In rarer cases, particularly with larger or deeper defects, an isthmocele has been linked to more serious complications including cesarean scar ectopic pregnancy, where a future pregnancy implants directly into the weakened niche, and a higher risk of scar rupture in a subsequent pregnancy. This is exactly why an isthmocele is worth discussing with your doctor before trying to conceive again, not something to leave unexamined.
WHAT ARE THE TREATMENT OPTIONS FOR ISTHMOCELE?
Treatment depends on your symptoms and whether you want to have more children. For women not planning further pregnancies, hormonal treatment such as combined oral contraceptives can reduce bleeding by suppressing the menstrual cycle. For women with bothersome symptoms or fertility concerns, surgical repair is an option, most commonly through hysteroscopic resection or laparoscopic repair. A study on laparoscopic repair technique reported symptom improvement in nearly 77% of patients and restored fertility in 73% of those trying to conceive afterward, without serious complications in the group studied.
DOES ISTHMOCELE AFFECT FUTURE PREGNANCIES OR VBAC?
It can. A larger isthmocele thins the uterine wall at exactly the point where a future labor would put the most pressure, which is part of why doctors evaluate scar quality carefully when discussing vaginal birth after cesarean (VBAC) eligibility for a subsequent birth. This is also why an ultrasound assessment of your scar is a reasonable thing to request if you are considering a vaginal birth after your previous c-section.
CAN ISTHMOCELE BE PREVENTED?
Not entirely, but surgical technique appears to matter. Research points to factors like a two-layer closure of the uterine incision, rather than a single layer, along with avoiding labor complications and infection, as ways to reduce the risk of a defect forming. Multiple prior c-sections also increase the severity of any isthmocele that does form, which is one more reason unnecessary repeat c-sections carry a real downstream cost.
WHEN SHOULD YOU SEE A DOCTOR?
• Spotting that continues more than 2 to 3 days after your period ends
• Bleeding between menstrual cycles
• Ongoing pelvic pain or discomfort
• Difficulty conceiving after a previous pregnancy
CONCLUSION
An isthmocele is a real, well documented, and treatable cause of postmenstrual bleeding, pelvic pain, and secondary infertility after a c-section, yet it remains something very few women are told to watch for. If your period never quite seems to end or you notice repeated brown spotting after your cycle, it is worth discussing this possibility with your doctor rather than assuming it is normal.
If you are also weighing whether a vaginal birth is possible after your c-section, I would encourage you to read my article on VBAC, since scar quality is one of the factors that connects directly to this topic.
DISCLAIMER
This article is for educational purposes only and is not a substitute for professional medical advice. Always consult a qualified healthcare provider about abnormal bleeding, pelvic pain, or fertility concerns following a c-section.
REFERENCES
• A Systematic Review on Caesarean Niche and Postmenstrual Spotting Syndrome: The Scar That Speaks.” Cureus, 2025. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12766140/
• Isthmocele: an overview of diagnosis and treatment.” PubMed, 2019. https://pubmed.ncbi.nlm.nih.gov/31166450/
• Incidence of Uterine Cesarean Scar Niche After Cesarean Delivery and Assessment of Its Risk Factors.” PMC, 2025. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12471730/
• Outcomes of Laparoscopic Cesarean Scar Defect Repair: Retrospective and Observational Study.” PMC, 2023. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10254061/
