Uterine Anomalies & Septum

Congenital uterine anomalies are differences in the shape of the womb that you are born with. They happen because the uterus forms in the womb from two tubes (the Müllerian ducts) that fuse in the middle and then resorb the wall between them. If that process is incomplete, the uterus ends up with an unusual shape. A systematic review estimated these anomalies in about 5.5% of unselected women, so they are more common than many people realise (Chan, 2011).

The European societies ESHRE and ESGE published a widely used classification that groups anomalies by how the uterus formed: septate, bicornuate, unicornuate, didelphys, and the very mild arcuate shape (Grimbizis, 2013). A septate uterus has a normal outer shape but a wall of tissue dividing the cavity inside. A bicornuate uterus has two horns with a dip in the outer surface, didelphys is a full duplication, and unicornuate has just one developed side.

Uterine anomalies are present from birth, so there is nothing you did or did not do to cause them. They arise during early fetal development, when the two Müllerian ducts either fail to fuse properly (giving bicornuate or didelphys shapes), fail to develop on one side (unicornuate), or fuse but do not fully resorb the dividing wall (the septate uterus). The arcuate shape is the mildest version, where only a small dip in the cavity remains.

There is no single gene or exposure that explains most cases, and the condition is not something you inherit in a simple way. Because the kidneys and reproductive tract develop side by side, some women with a uterine anomaly, especially unicornuate or didelphys, also have a missing or misplaced kidney, so doctors often check the kidneys when one of these shapes is found.

Most women with a uterine anomaly have no symptoms at all, and many are only discovered during fertility tests, a scan in pregnancy, or investigation after a miscarriage. A normal period and a normal pregnancy are both entirely possible with several of these shapes, so the absence of symptoms is reassuring rather than alarming.

When problems do appear, they usually relate to pregnancy rather than to daily life: recurrent early miscarriage, preterm birth, or a baby lying in an awkward position late in pregnancy. The septate uterus in particular is the shape most strongly associated with first-trimester pregnancy loss (Chan, 2011). Some anomalies, such as an obstructed horn, can also cause painful periods, but this is less common.

The single most useful test is three-dimensional (3D) transvaginal ultrasound, because it shows both the inside cavity and the outer surface of the uterus at the same time. That outer view is what separates a septate uterus (smooth outline, inner wall) from a bicornuate uterus (a notch in the outer surface), and the two are managed very differently, so getting this distinction right matters.

A standard 2D ultrasound or an HSG (dye X-ray of the tubes) can suggest an anomaly but cannot reliably tell septate from bicornuate on its own. MRI gives an excellent map of the anatomy and is used when 3D scanning is unclear or when surgery is being planned. Hysteroscopy, a thin camera inside the uterus, confirms a septum from the inside and is also the route used to treat it. The ESHRE/ESGE system provides agreed definitions so different clinics describe the same shape the same way (Grimbizis, 2013).

Standard Diagnostic Tests in India

• 3D transvaginal ultrasound — The preferred test, showing the inner cavity and the outer surface together so septate and bicornuate shapes can be told apart.
• MRI — A detailed anatomical map used when 3D ultrasound is unclear or when surgery is being planned.
• Hysteroscopy — A thin camera inside the uterus confirms a septum from within and is also the route used to cut it.
• HSG (dye X-ray) — Can suggest an anomaly and checks the tubes, but cannot reliably distinguish septate from bicornuate on its own.

The effect on fertility depends heavily on which shape you have, and the impact is mostly on carrying a pregnancy rather than on getting pregnant. Anomalies are found in about 8% of infertile women, rising to roughly 13.3% of women with recurrent miscarriage and around 24.5% in women with both miscarriage and infertility (Chan, 2011). That said, the arcuate shape, the most common finding, behaves much like a normal uterus.

The septate uterus is the one most clearly linked with poorer outcomes. A systematic review found it was associated with a higher risk of first-trimester miscarriage and preterm birth (Chan, 2011). Unicornuate and didelphys uteri carry a higher chance of preterm birth and malpresentation, while many women with these shapes still have successful pregnancies. The key point is that having an anomaly does not automatically mean you cannot conceive or carry.

• Septate: highest risk of loss: The shape most strongly associated with first-trimester miscarriage and preterm birth in systematic review data.
• Arcuate: minimal impact: The mildest and most common finding, generally behaving much like a normal uterus.
• Unicornuate and didelphys: Carry a higher chance of preterm birth and the baby lying in an awkward position, though many pregnancies still succeed.
• Mainly about carrying, not conceiving: Most anomalies affect pregnancy continuation rather than the ability to get pregnant in the first place.
• More common in high-risk groups: Found in about 13.3% of women with recurrent miscarriage and around 24.5% with both miscarriage and infertility.

Most uterine anomalies need no surgery. Bicornuate, unicornuate, didelphys, and arcuate shapes are generally managed by careful monitoring during pregnancy rather than by operating, because surgery on these does not have good evidence of benefit and carries real risk. The one shape where surgery is genuinely discussed is the septate uterus, where the dividing wall can be cut with hysteroscopy, a day procedure with no abdominal cut.

Here, honesty about the evidence matters. The septum resection has long been offered for recurrent loss, but a multicentre randomized controlled trial (the TRUST trial) found that resection did not improve live birth compared with simply waiting, with live birth in 31% of the surgery group versus 35% of the expectant group (Rikken, 2021). Before that trial, a Cochrane review noted there were no randomized studies at all to support the operation (Rikken, 2017). So the decision is now far more individual, weighing limited proven benefit against the small risks of surgery.

A uterine anomaly does not stop you doing IVF, and for many shapes it changes very little about the egg-collection part of treatment. The eggs and embryos are made the same way; the anomaly mainly affects where and how an embryo can implant and grow. Your doctor will define the exact shape with 3D ultrasound or MRI before transfer so the plan fits your anatomy.

For most non-septate shapes, the approach is to proceed with IVF and then watch the pregnancy more closely for preterm birth and the baby's position. For a septate uterus, whether to resect the septum before an IVF transfer is now an open question rather than an automatic step, given that the randomized TRUST trial showed no clear improvement in live birth from surgery (Rikken, 2021). The ASRM guideline likewise stresses that the evidence for septum surgery improving outcomes is limited (ASRM, 2016). Discuss the trade-offs with your specialist rather than assuming surgery is required.