Key takeaways:
- Standardized second-trimester ultrasound screening with third-trimester confirmation detected 97.8% of vasa previa cases across more than 770,000 pregnancies.
- Screening demonstrated near-perfect diagnostic performance, with pooled sensitivity and specificity of 1.00 and very low false-positive and false-negative rates.
- Prenatal diagnosis of vasa previa was associated with high perinatal survival, with a pooled survival rate of 98.15%.
- Universal screening and targeted screening both showed high detection and survival rates, though data for targeted screening were limited.
- Because up to 20% of vasa previa cases occur without identifiable risk factors, routine screening may reduce missed diagnoses and prevent perinatal deaths.
Vasa previa is a rare but life-threatening obstetric condition, and evidence from a large systematic review indicates that standardized prenatal screening can identify nearly all affected pregnancies and is associated with high perinatal survival.1
Vasa previa occurs when unprotected fetal blood vessels traverse the membranes over or near the cervix.2 Rupture of these vessels during labor or membrane rupture can result in rapid fetal hemorrhage and death.1 Although vasa previa complicates approximately 1 in 1200 pregnancies, undiagnosed cases carry a high risk of stillbirth or neonatal death.
"There is considerable controversy about whether to screen for [vasa previa] prenatally... However, approximately 15% to 20% of cases of VP have no risk factors and thus may be missed by targeted screening," wrote investigators.
Clarifying the value of structured prenatal screening
The objective of this systematic review and meta-analysis was to evaluate the accuracy of standardized second-trimester ultrasound screening for vasa previa, with confirmation in the third trimester, and to estimate perinatal survival in screened populations. Cohort studies were eligible if they implemented a prospective, standardized second-trimester ultrasound screening protocol for vasa previa, either universally or in targeted high-risk populations, with confirmation later in pregnancy.
Standardized screening protocols included routine assessment of placental cord insertion, systematic evaluation of the region overlying the cervix using grayscale ultrasound or color Doppler, transvaginal ultrasound in patients with risk factors, and follow-up imaging for placenta previa or low-lying placenta. Only cases of vasa previa persisting to delivery were included.
Databases searched included MEDLINE, Embase, Web of Science, Global Health, and Global Index Medicus from inception through February 16, 2024. Two independent reviewers performed study selection, data extraction, and risk-of-bias assessment using the QUADAS-2 tool.
Detection accuracy across nearly 780,000 pregnancies
Nineteen cohort studies met inclusion criteria, representing 779,845 screened pregnancies. A total of 505 pregnancies were complicated by vasa previa at delivery, corresponding to an incidence of approximately 1 in 1544. Of these cases, 494 were diagnosed prenatally, yielding a detection rate of 97.8%.
Meta-analysis demonstrated a pooled sensitivity of 1.00 (95% CI, 0.99–1.00) for second-trimester screening with third-trimester confirmation, with no observed heterogeneity across studies. Sensitivity remained high in both universal and targeted screening protocols, although confidence intervals were wider in the targeted subgroup because of fewer included studies.
Specificity was also high. Among nearly 775,000 pregnancies evaluated for false-positive results, only 11 false-positive diagnoses were reported. The pooled specificity was 1.00 (95% CI, 1.00–1.00), indicating that standardized screening protocols rarely identified vasa previa incorrectly.
Survival outcomes following prenatal diagnosis
Perinatal survival among prenatally diagnosed cases ranged from 87.5% to 100% across individual studies. The pooled perinatal survival rate was 98.15% (95% CI, 88.30%–100.00%). Survival estimates were similar between universal and targeted screening approaches, although interpretation was limited by the small number of targeted-screening studies.
Sensitivity analyses excluding studies with higher risk of bias did not meaningfully change the results, suggesting that findings were robust. These findings indicate that standardized second-trimester ultrasound screening for vasa previa is feasible in diverse clinical settings and is associated with high diagnostic accuracy and excellent perinatal outcomes.
"We therefore recommend that national and societal guidelines for obstetric imaging be updated to include universal screening for [vasa previa]," wrote investigators.
References
- Donovan B, Bonanni G, Javinani A, et al. Ultrasound screening for vasa previa: a systematic review and meta-analysis. American Journal of Obstetrics & Gynecology. 2025;233(6):591-603. doi:10.1016/j.ajog.2025.08.003
- Oyelese Y, Javinani A, Shamshirsaz AA. Vasa previa. Obstetrics & Gynecology. 2023;142(3):503-518. doi:10.1097/AOG.0000000000005287
