Background Neurofibromatosis type 1 is a disorder characterized by café-au-lait spots and neurofibromas. Recent studies have suggested that neurofibromatosis type 1 may induce vascular fragility. Limited information is currently available on vascular fragility in pregnancies complicated by neurofibromatosis type 1. Case The patient was a 40-year-old woman (gravida 3, para 1) with neurofibromatosis type 1. In her second pregnancy, blood pressure began to rise at 30 weeks of gestation. At 34 weeks of gestation, left intercostal artery rupture and massive hemothorax occurred, resulting in neonatal death. In her third pregnancy, caesarean section was performed at 30 weeks of gestation prior to the expected increase in blood pressure, resulting in a livebirth. However, the patient died three months later due to left intercostal artery rupture. Conclusion Pregnancy complicated by neurofibromatosis type 1 is associated with vascular fragility, leading to fatal events. Thus, obstetricians should be aware of this condition. A management strategy needs to be established for vascular fragility in complicated pregnancy.