We report a case of diamniotic dichorionic pregnancy at 21 weeks and 5 days of gestation with threatened preterm labor with cervical modification and protrusion into vagina of the amniotic sac of twin one. After 4 days there was a rupture of membrane of the protruding sac and delivery of the first twin. We decided to retain the other one to allow improvement in the outcome for the second twin. The patient was treated with tocolytics, antibiotics and continuously monitored. After 18 days there was increasing uterine contractility and we decided to perform the cesarean section and delivered the second twin.