Prenatal diagnosis and management of vasa previa: a 6-year review

To evaluate the methods of screening and prenatal diagnosis of vasa previa.

We reviewed cases of vasa previa in our hospital between January 2002 and December 2007. During this period, we visualized the site of cord insertion using transabdominal ultrasonography and observed the internal os using gray-scale transvaginal ultrasonography. A diagnosis of vasa previa was confirmed by transvaginal color Doppler imaging.

We encountered 10 cases of vasa previa among 5131 deliveries. All cases had one or more known risk factors. In all of the four cases that underwent screening in the second trimester (i.e. between 20 and 25 weeks of gestation), the diagnosis was correct. Routine ultrasonography detected in only three of the other six cases of vasa previa that were referred to our hospital after 26 weeks of gestation. Of the other three cases referred after 26 weeks of gestation, in two cases vasa previa was detected by detailed examination using color Doppler transvaginal ultrasonography after fetal heart rate monitoring detected the presence of non-reassuring fetal status; in the remaining case, we were unable to make an antenatal diagnosis. Non-reassuring fetal status was seen on fetal heart rate monitoring in four of the five detected cases complicated by preterm labor.

We consider that the best timing of antenatal screening for vasa previa is the second trimester. Non-reassuring fetal heart rate pattern without other possible causes warrants detailed examination of vasa previa.