Background: The unique clinical syndrome of uterus didelphys, obstructed hemivagina, and ipsilateral renal anomaly is very rare and can be quite difficult to recognize because of the enormous heterogeneity in its clinical presentation. There are few long-term reports of the reproductive performance of women with this syndrome following treatment, or about the location of subsequent pregnancies. Case: A case in which two spontaneous pregnancies occurred alternatively in both hemiuteri: one despite a previous ipsilateral large hematometra and hematocolpos and the other, 8 years after, simultaneously with contralateral hematometra and hematocolpos (because of vaginal restenosis), is reported. Drainage of hematocolpos was performed at 14 weeks of pregnancy with immediate pain relief. Results: Pregnancy proceeded without complications. Eight month after delivery, a vaginoplasty was performed by excising the longitudinal vaginal septum, and marsupializing the vaginal cuff. Conclusions: This case highlights the importance of a correct and early diagnosis of developmental anomalies of the urogenital tract, as well as how a conservative approach in a Mü llerian anomaly with unilateral obstruction led to two successful pregnancies occurring alternatively in the unaffected and in the previously blocked side. This is additional information supporting that every effort should be made to preserve the obstructed uterus. ( J GYNECOL SURG 28:365)