Bicornuate Uterus

Bicornuate uterus is a congenital Müllerian fusion anomaly in which the uterine fundus is indented by more than 1 cm. It produces two separate uterine horns with a common lower segment and a single cervix. It results from partial failure of fusion of the Müllerian ducts.

It accounts for about 10 to 39 percent of uterine anomalies and is found in about 0.4 percent of women. Renal anomalies occur in about 5 percent.

• Bicornuate unicollis has one cervix.
• Bicornuate bicollis has two cervices (often with a longitudinal vaginal septum).

The fundal contour is concave or heart shaped and the external fundal cleft exceeds 1 cm. This distinguishes it from the septate uterus, where the external contour is flat or minimally indented (less than 1 cm) and the interior has a fibrous or muscular septum.

• Often asymptomatic and discovered during imaging, at caesarean section or at hysterosalpingography.
• Reproductive: second trimester loss, preterm labour (about 15 to 25 percent), fetal malpresentation (breech in over 25 percent, transverse lie), cervical insufficiency, fetal growth restriction, and caesarean delivery. Miscarriage risk is 25 to 30 percent and live birth rates are 60 to 70 percent.
• Menstrual function is usually normal; dysmenorrhoea and menorrhagia are occasional.
• Examination: normal; a heart shaped fundus may be felt on bimanual examination in a thin patient.

• Three dimensional pelvic ultrasound is the preferred first test, giving an accurate view of the external and internal fundal contours (fundal cleft greater than 1 cm, with divergent horns and a normal cavity or an angle between horns exceeding 90 degrees).
• MRI pelvis: gives detailed information on the fundal contour and cavity and is the best tool when ultrasound is inconclusive, to distinguish bicornuate from septate uterus, which matters for treatment.
• Hysterosalpingography shows two separate cavities with a wide intercornual angle (above 105 degrees) but does not show the external contour.
• Combined laparoscopy and hysteroscopy are done for definitive classification when the decision on surgery depends on it.
• Renal tract ultrasound to look for associated anomalies.

• Asymptomatic women need no treatment. Counsel about the pregnancy risks, and do surveillance.
• Surgery is not indicated for most women because the outcome of pregnancy is acceptable without it.
• Strassman metroplasty (unification of the two horns by transverse incision of the medial walls and sagittal closure) is reserved for women with recurrent second trimester loss or preterm births (two or more) with no other cause.
• It is done laparoscopically or by laparotomy with a vasopressin injection (0.2 units/mL, up to 20 units) to reduce blood loss, and closure in layers.
• Pregnancy rates after metroplasty are around 50 to 70 percent, with live birth rates of 70 to 85 percent in the group with previous losses. Deliver by caesarean section after metroplasty to avoid rupture, at 36 to 37 weeks.
• Cervical cerclage: indicated for a short cervix (below 25 mm before 24 weeks) or a history of cervical insufficiency. Use transvaginal ultrasound cervical length surveillance every 2 weeks from 16 to 24 weeks.
• Progesterone (micronised vaginal progesterone 200 mg daily or 90 mg gel daily from 16 to 36 weeks) is used when the cervix is short.
• Antenatal care: early ultrasound to confirm location, growth scans from 28 weeks, and recognition of malpresentation. External cephalic version is less successful.
• Delivery: vaginal birth is possible with cephalic presentation. Caesarean section for malpresentation, previous uterine surgery or obstetric indications.
• A bicornuate uterus contracts less effectively, so the risk of postpartum haemorrhage is raised. Use active management of the third stage, with oxytocin 10 units intramuscularly and tranexamic acid 1 g intravenously available.
• Fertility treatment: assisted reproduction is not hindered by the anomaly. Single embryo transfer is advised to reduce the multiple pregnancy risk.