Frequency of spontaneous resolution of vasa previa with advancing gestational age

By on January 6, 2020

Vasa previa, defined as unprotected fetal vessels running through the membranes over the cervix, often ruptures when the membranes rupture, frequently leading to sudden fetal death. This used to be a feared condition among obstetricians, first because of its devastating consequences, but also because, until recently, it was rarely diagnosed prior to the rupture and hence was considered unpreventable. There are now several studies that have documented universally excellent outcomes when vasa previa is diagnosed prenatally, and planned cesarean delivery is undertaken before the membranes rupture. Risk factors for vasa previa include a second-trimester low lying placenta/placenta previa (regardless of resolution), pregnancies with bilobed or succenturiate-lobed placentas, pregnancies resulting from in vitro fertilization, and multifetal pregnancies. Based upon our prior publication from 2014 (Rebarber A, et al JUM) we have recommended targeted screening in pregnancies in which these risk factors are present. Most recently, our current publication (Klahr et al AJOG 2019) found an absence of risk factors in 6% of cases of vasa previa, so we routinely advocate the region over the cervix should also be examined carefully and judicious evaluation with Color Doppler is advised. Additonally, in our  most recent publication on this topic we noted that a proportion of cases diagnosed in early pregnancy will resolve prior to delivery.  Our findings mean that women with vasa previa diagnosed early in pregnancy may not necessarily need hospitalization and early delivery and serial evaluation is important to properly diagnose patients that require cesarean section and early intervention. More specifically, we found that 39% of vasa previas diagnosed patients in our population (at Carnegie Imaging for Women , NYC) resolved over the course of pregnancy. Earlier gestational age at diagnosis, vasa previa not covering the internal os, and not having a resolved placenta previa all are associated independently with an increased likelihood of vasa previa resolution.

We also proudly note that our paper was highlighted in the December 2019 American Journal of Obstetrics and Gynecology Editorial titled “Vasa previa: time to make a difference” providing evidence that standard screening for this condition should be implemented nationwide as we have done since 2005 in our ultrasound units. A unique opportunity exists to prevent perinatal mortality from this condition. Prenatal diagnosis accompanied by timely cesarean delivery will prevent deaths from vasa previa.

Maternal Fetal Medicine blogs are intended for educational purposes only and do not replace certified professional care. Medical conditions vary and change frequently. Please ask your doctor any questions you may have regarding your condition to receive a proper diagnosis or risk analysis. Thank you!

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