734: Prevalence of obstetric risk factors in pregnancies with vasa previa: A systematic review and meta- analysis

Abstract

To review existing literature and calculate the prevalence of vasa previa and its known risk factors in affected pregnancies. We conducted a systematic review of observational studies in accordance with the Meta-analysis of Observational Studies in Epidemiology (MOOSE) guidelines. Five databases, Medline, Embase, the Cochrane Library, PubMed and www.clinicaltrials.gov were searched and only studies describing more than five cases of vasa previa were included. Two reviewers independently carried out title and abstract screening and data extraction from included full-texts. Disagreements were resolved through discussion. The references of included papers were screened to identify articles missed by the initial literature search. We performed DerSimonian-Laird binary random- effects meta-analyses using OpenMetaAnalyst, presenting pooled proportions with 95% confidence intervals (CI), of the prevalence of risk factors in cases of vasa previa. We included 22 studies that reported 447 pregnancies with vasa previa out of 1,121,792 deliveries (0.43 cases of vasa previa per 1000 deliveries). The prevalence of known risk factors for vasa previa included a low-lying placenta [61.5% (53.0-70.0%)], velamentous cord insertion [52.7% (41.1-64.3%)], bilobed or succenturiate lobed placenta [32.7% (21.1-44.3%)], the use of any assisted reproductive technique [28.2% (20.1-36.3%)] (including in-vitro fertilization [26.4% (16.0-36.8%]), and multiple gestation [9.10% (5.6-12.6%)]. These studies fared well on risk of bias assessment. Although prenatal diagnosis of vasa previa has been shown to improve obstetrical and neonatal outcomes with a prevalence of 0.43 per 100 pregnancies, population-based screening may not be cost-effective. However, a policy of screening pregnancies at increased risk for vasa previa may be a reasonable option, the clinical and cost-effectiveness of which needs to be determined.View Large Image Figure ViewerDownload Hi-res image Download (PPT)