Abstract: BACKGROUND: There is no consensus on managing pregnancy when the fetus is diagnosed with idiopathic premature constriction or closure of the ductus arteriosus (PCDA). Knowing whether the ductus reopens is valuable information for managing idiopathic PCDA. We conducted a case-series study to investigate the natural perinatal course of idiopathic PCDA and examined factors associated with ductal reopening. METHODS: We retrospectively collected information about the perinatal course and echocardiographic findings at our institution, which, on principle, does not determine delivery timing based on fetal echocardiographic results. We also examined perinatal factors related to the reopening of the ductus arteriosus. RESULTS: Thirteen cases of idiopathic PCDA were included in the analysis. The ductus reopened in 38% of cases. Among cases diagnosed in < 37 weeks of gestation, 71% reopened, which was confirmed seven days after diagnosis (interquartile range 4–7). Diagnosis earlier in gestation was associated with ductal reopening (p = 0.006). Two cases (15%) developed persistent pulmonary hypertension. No fetal hydrops or death occurred. CONCLUSIONS: The ductus is likely to reopen when prenatally diagnosed before 37 weeks gestation. There were no complications due to our pregnancy management policy. In idiopathic PCDA, especially if the prenatal diagnosis is made before 37 weeks of gestational age, continuing the pregnancy with careful monitoring of the fetus’s well-being is recommended.