Current Evidence on Vasa Previa without Velamentous Cord Insertion or Placental Morphological Anomalies (Type III Vasa Previa): Systematic Review and Meta-Analysis

Abstract

Vasa previa carries a high risk of severe fetal morbidity and mortality due to fetal hemorrhage caused by damage to unprotected fetal cord vessels upon membrane rupture. Vasa previa is generally classified into types I and II. However, some cases are difficult to classify, and some studies have proposed a type III classification. This study aimed to review the current evidence on type III vasa previa. A systematic literature search was conducted, and 11 articles (2011–2022) were included. A systematic review showed that type III vasa previa accounts for 5.7% of vasa previa cases. Thirteen women with type III vasa previa were examined at a patient-level analysis. The median age was 35 (interquartile range [IQR] 31.5–38) years, and approximately 45% were assisted reproductive technology (ART) pregnancies. The median gestational week of delivery was 36 (IQR 34–37) weeks; the antenatal detection rate was 84.6%, and no cases reported neonatal death. The characteristics and obstetric outcomes (rate of ART, antenatal diagnosis, emergent cesarean delivery, gestational age at delivery, and neonatal mortality) were compared between types I and III vasa previa, and all outcomes of interest were similar. The current evidence on type III vasa previa is scanty, and further studies are warranted.

Prenatal diagnosis and postnatal outcome of Type‐III vasa previa: systematic review of literature

“…Ultrasound Obstet Gynecol 2024; 63: [24][25][26][27][28][29][30][31][32][33] Published online in Wiley Online Library (wileyonlinelibrary.com). DOI: 10.1002/uog.26315.…”

“…In addition to the two well-described categories of VP, a third phenotype was reported recently, characterized by aberrant vessels leaving the placental surface and subsequently returning to the placental mass with a 'boomerang orbit', in the absence of a velamentous cord insertion or a bilobed/succenturiate placenta (Figure 5) 9,10,29,30 . In view of our findings, we would like to challenge this definition of Type-III VP: the presence of a velamentous cord insertion or succenturiate lobes does not define per se VP Type I and Type II, respectively, since aberrant vessels of Type-III VP can coexist along with placental or cord abnormalities, as long as these structures are not adjacent to the internal os and the aberrant vessel represents the only vascular structure in the lower uterine segment 12,[24][25][26] .…”

Vasa Previa: A Case Report from Tiom General Medical Hospital Lanny Jaya Regency, Papua-Indonesia

“…The risk to the fetus can be significantly decreased by having a cesarean section performed before the membranes rupture. (2), (3) Here, we describe a vasa previa that was unintentionally discovered during a physical examination and ultrasound while the patient was 39 weeks pregnant and exhibiting labor symptoms.…”

Evolution from placenta previa to Type‐3 vasa previa

“…A number of recent publications have described Type-3 vasa previa, a variant of vasa previa in which fetal vessels run unprotected over the cervix from one placental edge to another in a placenta that does not have a velamentous cord insertion or accessory lobes [1][2][3] . Because most cases of Type-3 vasa previa have a normal cord insertion, relying merely on the identification of a velamentous cord insertion or the presence of accessory lobes as risk factors for vasa previa will inevitably miss some cases, potentially leading to avoidable perinatal death.…”

“…In 2004, we described a variant of vasa previa in which there was a normal cord insertion and a single placental lobe, Oyelese but fetal vessels ran from one edge of the placenta to another 10 . This was subsequently termed 'Type-3 vasa previa' [1][2][3] . We hypothesized that this variant arose from placenta previa in early pregnancy, followed by atrophy of the placental tissue overlying the cervix, leaving behind unprotected fetal vessels running over the cervix 10 .…”