LAUSR

BACKGROUND Vasa previa is a serious obstetric complication that can result in fetal hemorrhage and demise upon spontaneous labor. Suggested management for vasa previa is elective hospitalization and caesarean delivery prior to spontaneous labor. There is little reported evidence of the rate of vasa previa resolution over the course of gestation. Identification of the resolution rate and of factors predictive of resolution could potentially improve clinical management and patient counseling. OBJECTIVE To identify the resolution rate of vasa previa across gestation and to determine clinical and sonographic factors that are associated with vasa previa resolution. STUDY DESIGN We conducted a retrospective cohort study of all women diagnosed with vasa previa in a single ultrasound unit between 2005 and 2018. Vasa previa was defined as a fetal vessel within 2 cm of the internal cervical os on transvaginal sonography. The primary outcome was vasa previa resolution, defined as migration of the vasa previa to > 2 cm away from the internal os. RESULTS One hundred women with vasa previa were included, diagnosed at a mean gestational age (GA) of 22.8 +/- 4.9 weeks. Thirty-nine women (39.0%, 95% CI 30% - 49%) had resolution of vasa previa at a mean gestational age of 28.6 +/- 4.7 weeks. Factors associated with vasa previa resolution were earlier GA at diagnosis (aOR 6.10, 95% CI 1.92-19.40), vasa previa not covering the internal os at diagnosis (aOR 8.29, 95% CI 2.79-24.62) and vasa previa not being the result of a resolved placenta previa (aOR 2.85, 95% CI 1.01-8.03). One woman with a dichorionic twin pregnancy and vasa previa resolution (at 31 weeks, fetal vessels located 2.8 cm from the internal os) presented at 33 weeks with massive bleeding and fetal demise of twin A. It was unclear if the demise was related to vasa previa or placental abruption. CONCLUSIONS 39% of vasa previas in our population resolved over the course of pregnancy. Earlier GA at diagnosis, vasa previa not covering the internal os, and not having a resolved placenta previa are all independently associated with an increased likelihood of vasa previa resolution. Women with vasa previa should be followed serially to assess for vasa previa resolution, as many will resolve in the third trimester.