bicornuate uterus

The uterus, cervix, and upper two-thirds of the vagina derive from the paired paramesonephric (Mullerian) ducts, which fuse in the midline and then resorb the intervening septum. Incomplete fusion produces a bicornuate uterus, with an indented external fundal contour separating two endometrial cavities; failure of septal resorption instead produces a septate uterus, which has a normal external contour and is the commonest anomaly and the one most amenable to hysteroscopic resection. Complete failure of fusion gives uterus didelphys with two cervices. Because Mullerian and mesonephric development are linked, up to a third of patients have an associated renal anomaly, most often unilateral renal agenesis, so imaging of the urinary tract is indicated. Obstetric risks include recurrent second-trimester loss, preterm labour, cervical insufficiency, breech and transverse lie, and increased caesarean delivery. MRI or three-dimensional ultrasound distinguishes bicornuate from septate by assessing the external fundal contour.