During pregnancy, patients with unicornuate uterus should be monitored due to risk of premature rupture of membranes and preterm birth secondary to cervical incompetence. They must undergo periodic cervical ultrasound evaluation for surveillance cervical shortening. In some cases placement of a cervical cerclage is indicated. Another obstetrical complication frequently seen in patients with unicornuate uterus is fetal malpresentation.
In women with uterus unicornuate type A1a, where there is a rudimentary uterus with a communicating endometrial cavity, there is the possibility that pregnancy implants in the rudimentary uterus. If the pregnancy progresses, growth of the rudimentary horn could result in uterine rupture in as high as 80-90% of cases which represent a life threatening event.
Congenital uterine anomalies are associated to urologic anomalies in about 40% of patients, being contralateral renal agenesis the most common reported in 16% of cases. Other malformations include ectopic kidney and pyelocalyceal duplicity.
The presence of the ovary in an ectopic location is also present in 42% of cases of unicornuate uterus. This occurs as a result of the lack of descent of the gonad into the pelvis. This ovarian migration occurs in the third month of conception, in which the ovaries migrate down from a position near the kidney to its final location. Ovarian ectopic location is difficult to diagnose, in which case MRI has proven to be the best imaging modality.
The diagnosis of this type of congenital uterine anomaly is usually incidental unless there is a functional non-communicating rudimentary horn (with endometrial cavity). In this case, the patients usually present with dysmenorrhea, which will increase from menarche, due to growing hematometra in the rudimentary horn.
A common finding is repetedly spontaneous abortio till the cavity grow sufficiently to mantein the pregnancy, but as you said, normally those pregnancies finishing with premature rupture of membranes and immature deliveries. In best cases after two or three abortions the patient delivers a premature new born with handicaped cappabilities to survive. A real russian roulette. It is or it is not a rule to perform a cerclage. In those complicated cases could be a solution a FIV-TE transfering the embryos to a surrogate uterus.