Are we over-diagnosing vasa praevia? The experience and lessons learned in a tertiary centre.

Background: Vasa praevia (VP) is a rare obstetric condition in which unprotected fetal vessels transverse the cervix, are vulnerable to rupture during labour and may result in rapid exsanguination of the fetus. Antenatal diagnosis of VP has resulted in excellent outcomes. However, there are little data available on the false positive rates for the antenatal diagnosis of VP. Improving accuracy of the diagnosis of VP can potentially improve outcomes and reduce unnecessary intervention.

Aims: To assess our accuracy in the diagnosis of VP, examine our false positive diagnoses of VP and suggest strategies during antenatal ultrasound to aid in the antenatal diagnosis of VP.

Material And Methods: We conducted a retrospective descriptive study of women diagnosed with VP antenatally over 11 years at a single tertiary hospital and eligible patients were identified from obstetric databases. All medical records, including ultrasound reports, were reviewed and compared with the placental histological findings and both operative and midwifery documentation of the cord insertion.

Results: Twenty-three women (25 babies) were diagnosed with VP and underwent a caesarean section delivery at a mean gestational age of 36 weeks. The false positive rate in our series was 17% (4/23).

Conclusions: Our study highlights the importance of postnatal confirmation of the diagnosis of VP and careful documentation of intraoperative findings of the placenta and cord insertion. We suggest strategies to aid in the accurate diagnosis of VP, thereby improving clinical decision-making and reducing unnecessary intervention.