Incidence and outcomes of vasa praevia in the United Kingdom.

BACKGROUND

Vasa praevia is an obstetric condition in which the fetal vessels run through the membrane over the internal cervical os, unprotected by the placenta or umbilical cord. It is associated with perinatal mortality if not diagnosed antenatally. We estimated the incidence and investigated outcomes of vasa praevia in the UK.

METHODS

We conducted a population-based descriptive study using the UK Obstetric Surveillance System (UKOSS). Cases were identified prospectively through monthly UKOSS submissions from all UK hospitals with obstetrician-led maternity units. All women diagnosed with vasa praevia who gave birth between 1st December 2014 and 30th November 2015 were included. The main outcome was estimated incidence of vasa praevia with 95% confidence intervals, using 2015 maternities as the denominator.

RESULTS

Fifty-one women met the case definition. The estimated incidence of diagnosed vasa praevia was 6.64 per 100,000 maternities (95% CI 5.05-8.73). Of 198 units, 10 (5%) had a vasa praevia screening programme; one of these 10 units identified 25% of the antenatally diagnosed cases. Among women who had vasa praevia diagnosed or suspected antenatally (n=28, 55%), there were no perinatal deaths or hypoxic ischaemic encephalopathy (HIE). Twenty-four women with antenatal diagnosis were hospitalised at a median 32 weeks' gestation and caesarean section was scheduled at a median 36 weeks' gestation. When vasa praevia was diagnosed peripartum (n=23, 45%), the perinatal mortality rate was 37.5% and 47% of survivors developed HIE.

CONCLUSIONS

The incidence of diagnosed vasa praevia was lower than anticipated. There was high perinatal mortality and morbidity for cases not diagnosed antenatally. The incidence of antenatally identified cases was much higher in the few centres that actively screened for this condition, and the perinatal outcomes were better. However, this group were all delivered by caesarean section and may include women who would not have experienced any adverse perinatal outcome.