Prenatal diagnosis of vasa praevia in routine clinical practice: Prevention of stillbirths and impact on perinatal outcomes

Background: Vasa praevia (VP) is defined as the presence of unsupported fetal blood vessels in close proximity of the internal os of the cervix. There is robust evidence from observational cohort studies and meta-analysis that prenatal diagnosis of VP is associated with excellent perinatal outcomes. We have previously proposed a two-stage strategy for prenatal diagnosis that can be implemented in routine clinical practice leading to effective prenatal diagnosis and prevention of fetal and neonatal mortality and morbidity.

Objectives: To demonstrate the feasibility and effectiveness of a two-stage screening strategy for prenatal diagnosis of VP in routine clinical practice and to estimate the potential impact on prevention of stillbirths and perinatal deaths.

Study design: This was an observational retrospective cohort study carried out at the Medway Fetal and Maternal Medicine Centre between January 2010 and June 2022. We examined the feasibility and effectiveness of this policy in terms of identification of a high-risk cohort and prenatal diagnosis of VP through routine 11-13 and 20-22 weeks' ultrasound assessments based on the two-stage protocol. We also examined the impact on maternal, neonatal and perinatal outcomes in pregnancies with a confirmed diagnosis of VP. Absolute risks (95 %) were calculated based on rates of events in the two groups. Logistic regression analysis was used to estimate independent contribution from maternal and pregnancy characteristics in prediction of VP.

Results: The study population of 53,648 singleton pregnancies included 45 pregnancies with VP (0.83 per 1,000 pregnancies or an incidence of 1 in 1,192 pregnancies). VP was suspected in 56 cases and were resolved in 11 cases (19.6 %), thus leaving 45 pregnancies with a confirmed diagnosis of VP. The main findings that predicted VP included a low-lying placenta at 20-22 weeks', placenta praevia, bilobed placenta and a velamentous cord insertion. In our study population, pregnancies with a prenatal diagnosis of VP had a livebirth rate of 100 % and an intact perinatal survival rate of 97.8 %.

Conclusion: Our study demonstrates that effective prenatal diagnosis of pregnancies with VP can be achieved in routine clinical practice with good perinatal outcomes.