The Characteristics and Obstetric Outcomes of Type II Vasa Previa: Systematic Review and Meta-Analysis

Abstract

Vasa previa is a rare fetal life-threatening obstetric disease classified into types I and II. This study aimed to examine the characteristics and obstetric outcomes of type II vasa previa. A systematic review was performed, and 20 studies (1998-2022) were identified. The results from six studies showed that type II vasa previa accounted for 21.3% of vasa previa cases. The characteristics and obstetric outcomes (rate of assisted reproductive technology (ART), antenatal diagnosis, emergent cesarean delivery, maternal transfusion, gestational age at delivery, and neonatal mortality) were compared between type I and II vasa previa, and all outcomes of interest were similar. The association between ART and abnormal placenta (bilobed placenta or succenturiate lobe) was examined in three studies, and the results were as follows: (i) increased rate of succenturiate lobes (ART versus non-ART pregnancy; OR (odds ratio) 6.97, 95% confidence interval (CI) 2.45-19.78); (ii) similar rate of abnormal placenta (cleavage-stage versus blastocyst embryo transfer); (iii) increased rate of abnormal placenta (frozen versus fresh embryo transfer; OR 2.97, 95%CI 1.10-7.96). Although the outcomes of type II vasa previa appear to be similar to those of type I vasa previa, the current evidence is insufficient for a robust conclusion.

Keywords: accessary lobes; assisted reproductive technique; bilobed placenta; succenturiate lobes; type II vasa previa; vasa previa.

Figure 1

Study selection scheme of the systematic search of previous studies. Abbreviation: VP, vasa previa.

Figure 2

Meta analysis of the characteristics and outcomes of type I and type II vasa previa. The pooled odds ratios for (A) the rate of ART (unadjusted), (B) the rate of antenatal diagnosis (unadjusted), (C) the rate of emergent cesarean delivery (unadjusted), and (D) gestational age at delivery between women with type I and type II vasa previa are shown. Forest plots were ordered by the year of publication and relative weight (%) of the study within the strata. The heterogeneity among the studies in each analysis was as follows: substantial heterogeneity (A: I² = 64%) in the unadjusted analysis, no heterogeneity (B: I² = 0%) in the unadjusted analysis, low heterogeneity (C: I² = 23%) in the unadjusted analysis, and substantial heterogeneity (D: I² = 70%) in the unadjusted analysis. The above results were calculated using RevMan ver. 5.4.1 and may differ slightly from the original values. Abbreviations: CI, confidence interval; ART, assisted reproductive technology; Emergent CD, emergent cesarean delivery; GA, gestational age.

Figure 3

A hypothesis of the increased rate of type I and type II vasa previa in ART pregnancy. Reproduced and updated the data from Biomedicines. 2022 Jul 17; 10 (7): 1722. Matsuzaki S et al. [54]. (A) The combination of velamentous cord insertion and low-lying placenta is a high-risk condition of vasa previa. (B) Abnormal placenta such as bilobed placenta or the placenta with a succenturiate lobe is a risk factor of type II vasa previa. (C) Women with ART are more likely to have velamentous cord insertion and low-lying placenta compared to those without ART pregnancy. Increased rate of velamentous cord insertion and low-lying placenta may lead to the increased rate of type I vasa previa. (D) ART may be associated with the higher incidence of abnormal placenta. This may lead to the increased rate of type II vasa previa. Abbreviations: VP, vasa previa; ART, assisted reproductive technology; VCI, velamentous cord insertion; LLP, low-lying placenta; ↑, increase; ↑↑, markedly increase.