Vasa previa is defined as aberrant fetal blood vessels crossing over or within 2 cm of the internal cervical os. These blood vessels are unprotected by the umbilical cord or placenta and run through the amniotic membranes¹.

There are two types of vasa previa. Type 1 occurs when abnormal fetal vessels connect a velamentous cord insertion to the main body of the placenta. Type 2 occurs when fetal vessels connect a bilobed placenta or a placenta with succenturiate lobe¹.

Vasa previa is a rare but potentially catastrophic cause of antepartum haemorrhage and can result into fetal death. When diagnosed prenatally, it can make a major impact on the management of these cases².

Australasian Sonographers Association (ASA) has released guidelines in May 2020 on vasa previa diagnosis in mid trimester ultrasound, which mentions that a dynamic sweep of the transducer with colour Doppler over the lower uterine segment should be performed and documented at every mid trimester ultrasound³.

We have performed an audit to assess our practice regarding the assessment of vasa previa with a dynamic sweep of the transducer over the lower uterine segment.

The aim of the audit is to raise awareness amongst the sonographers regarding the new ASA guidelines and improve our efficacy in the diagnosis of vasa previa.