We report a case of a rudimentary horn pregnancy with herniation of a fetal arm and umbilical cord into the main uterine cavity that presented as an incidental finding on a routine second-trimester ultrasound scan. We also review the literature that guides the diagnosis and management of these rare complicated pregnancies.
Unicornuate uterus with a rudimentary horn is a rare Müllerian anomaly that has a high incidence of obstetric complications that include ectopic pregnancy in the rudimentary horn. It occurs in approximately 1 of every 76,000 pregnancies, and most often presents with first- or second-trimester uterine rupture.
Case Report
A 38 year-old woman in her third pregnancy underwent a detailed anatomy survey at 21 weeks 4 days of gestation. Her obstetric history was significant for 2 uncomplicated vaginal deliveries at term. She denied a history of dysmenorrhea or of pain earlier in pregnancy. Ultrasound findings included a normally grown fetus in a cavity in the right fundal portion of the uterus, separated by an apparent uterine septum from a second larger cavity. The larger cavity contained most of the amniotic fluid, a fetal arm, and a large loop of umbilical cord. Three-dimensional ultrasound imaging ( Figure 1 ) and magnetic resonance imaging (MRI; Figure 2 ) clarified the ultrasound findings, which were consistent with a right rudimentary horn pregnancy communicating with the main uterine cavity.
The patient strongly desired expectant treatment. She presented at 24 weeks 3 day gestation with preterm premature rupture of membranes, a nonreassuring fetal heart rate tracing, and sonographic evidence of severe edema of the fetal arm. Cesarean delivery was performed, and a vertical uterine incision was made in the right rudimentary horn. Findings were consistent with antenatal imaging and included entrapment of the right arm, lower face, and umbilical cord with resultant edema. A male infant who weighed 650 g was delivered; because of deformation and edema of the lower face ( Figure 3 ), an airway could not be established. The infant died shortly after birth.
