We describe the effect of pregnancy on a woman with multiple pulmonary arteriovenous fistula. Pregnancy was terminated at 35 weeks' gestation because of severe hypoxemia. During the early postpartum period, the intrapulmonary shunt fraction enlarged, and hypoxemia worsened, necessitating emergency resection of the A-V fistula. Pregnancy may increase the intrapulmonary shunt fraction in patients with multiple pulmonary arteriovenous fistula through its effect on plasma volume and produce life-threatening hypoxemia near term or in the early postpartum period.