septate uterus
Summary
Septate uterus is the most common Müllerian duct anomaly, caused by failure of resorption of the fibrous/muscular septum that forms after the two Müllerian ducts fuse. It presents with a normal external uterine contour but a fibrous septum dividing the uterine cavity, leading to recurrent first-trimester pregnancy loss and infertility.
Detail
During embryogenesis, the paired Müllerian (paramesonephric) ducts fuse in the midline to form the uterus, cervix, and upper vagina. Normally, the medial septum between the fused ducts resorbs completely by the end of the first trimester. Failure of this resorption process results in a septate uterus, in which a fibrous or fibromuscular septum persists, partially or completely dividing the endometrial cavity while the external uterine fundal contour remains normal (convex or minimally indented, <1 cm), distinguishing it from a bicornuate uterus (which has an abnormal external fundal contour due to failure of fusion rather than failure of resorption).
Clinical significance: The septum is composed of poorly vascularized fibrous tissue, which provides an unfavorable environment for implantation and placentation, leading to the highest rate of pregnancy loss (especially first-trimester miscarriage) among all Müllerian anomalies. It is also associated with infertility, malpresentation, and preterm labor. Unlike other Müllerian anomalies, septate uterus is amenable to surgical correction.
Diagnosis: Best distinguished from bicornuate uterus using 3D transvaginal ultrasound, MRI, or hysterosalpingography combined with laparoscopy to assess the external fundal contour. Hysteroscopy alone shows the intracavitary septum but cannot assess the external contour.
Treatment: Hysteroscopic septum resection (metroplasty) is the treatment of choice, improving reproductive outcomes significantly, unlike bicornuate uterus which requires more invasive surgical correction (Strassman metroplasty) only in select cases.
Associations: Müllerian anomalies can co-occur with renal anomalies (e.g., unilateral renal agenesis) since the Müllerian and mesonephric (Wolffian) ducts develop in close association during embryogenesis.
Sources
- First Aid for the USMLE Step 1
- Williams Obstetrics, 25th ed.
- UpToDate: Congenital uterine anomalies: Clinical manifestations and diagnosis
- American College of Obstetricians and Gynecologists (ACOG) Practice Bulletins
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