A uterine niche, also called a Caesarean scar defect or isthmocele, is a small indentation in the uterine wall where a previous Caesarean section has healed.
Niches are relatively common after Caesarean delivery, and many women have no symptoms at all.
What problems can a niche cause?
In some women, menstrual blood can collect within the niche. This may cause prolonged brownish spotting after the period, pelvic discomfort or bleeding between periods.
A niche has also been associated with reduced fertility in some studies. However, this does not mean that every niche causes infertility.
Does every niche need surgery?
No. This is an important change in how uterine niches are managed.
Finding a niche on ultrasound does not automatically mean that it needs to be repaired. Current recommendations support a more individualized approach, and women without symptoms generally do not require treatment.
Even in women undergoing fertility treatment, there is currently insufficient evidence to recommend routine surgery simply because a niche is present.
When may a niche be important for fertility?
A niche may deserve closer attention when it is associated with:
- significant or prolonged postmenstrual spotting
- fluid collecting inside the uterine cavity
- otherwise unexplained secondary infertility
- a large niche or very thin remaining uterine muscle
Fluid inside the uterine cavity may be particularly important during IVF because it can potentially interfere with embryo implantation.
Does surgery improve fertility?
Surgery can improve niche-related symptoms in appropriately selected women. However, although niches have been associated with poorer IVF outcomes, we do not yet have strong evidence showing that repairing every niche improves the chance of a live birth.
Therefore, surgery should be considered when there is a specific clinical reason to treat the niche, rather than simply because one was found on ultrasound.
The key message
A uterine niche is a finding—not automatically a disease requiring surgery.
Management should depend on symptoms, fertility history, the appearance of the niche, the thickness of the remaining uterine muscle and whether fluid is present inside the uterine cavity.
The important question is no longer simply “Is there a niche?”, but rather:
“Is this niche actually causing a problem for this patient?”
– Dr Dziura
