Vasa previa: Another ultrasound sign and caution at cesarean section

We read with interest the article “Prenatal diagnosis of vasa previa” by Bręborowicz et al. [1]. They prenatally diagnosed vasa previa, which led to cesarean section. We have an addition and a concern.

Our addition is regarding the ultrasound diagnosis of vasa previa, one type of velamentous cord insertion. Although Bręborowicz et al. [1] did not give a detailed description of how they ultrasonographically diagnosed this condition as vasa previa, the manuscript suggests that the diagnosis was made by “identification of the placental cord insertion”. It was unfortunate that Bręborowicz et al. [1] did not cite our previous article regarding this issue [2]. Identification of cord insertion, its site and morphology, is not always easy, especially for a relatively inexperienced practitioner. We introduced a novel ultrasound sign, “mangrove sign”, to diagnose this condition [2]. As previously described, in velamentous cord insertion, the cord vessels branch into several large vessels soon after cord insertion into the fetal membranes [2]. These vessels run between the insertion site and placenta; these free aberrant vessels running on the fetal membranes are good signs for an ultrasound diagnosis of velamentous cord insertion, and thus vasa previa. Figure 1(a) indicates the mangrove sign: several large vessels run on the fetal membranes to the placental surface. Post-delivery examination of the placenta confirmed the diagnosis of velamentous cord insertion. Figure 1(b) is the trace of the placenta and cord of Bręborowicz et al.’s case [1] (their Figure 1C), whose pattern shows a marked similarity to Figure 1(a): some vessels run on the membranes and reach the placenta. Figure 1(c) is a photograph of a mangrove tree. The trunk represents the cord and the root branches represent free vessels, which reach the ground, the placenta. Although we have not yet examined the sensitivity and specificity of this sign to detect velamentous cord insertion, even a relatively inexperienced practitioner can easily identify the “mangrove sign” and, thus, identifying its presence has become part of our department’s protocol.

Figure 1. Velamentous insertion of the umbilical cord, its color Doppler image (a), schematic presentation of aberrant vessels of Bręborowicz et al.’s Figure 1C [1] (b) and a mangrove tree (c). (a) Color Doppler image of velamentous cord insertion, which was obtained from a 30-week ultrasound scan of a pregnant woman: who was later confirmed to have velamentous cord insertion and gave abdominal birth to an infant. The arrow indicates aberrant vessels running over the fetal membranes to the placental surface. (b) The figure of the cord and placenta of Bręborowicz et al.’s case (their Figure 1C [1]) mimics the color Doppler image of Figure 1(a). (c) A mangrove tree: the trunk represents the cord. The trunk branches into several roots, reaching the ground, which indicates the cord, aberrant vessels, and placental surface. The ultrasound image shown in Figure 1(a) resembles a mangrove tree, and thus we named this sign a “mangrove sign” [2].

Our concern regards the cesarean incision route of this case. Bręborowicz et al. [1] used the following technique: the uterine incision was gradually deepened to allow the membranes to bulge out from the incision while they remained intact, which enabled the determination of the course of aberrant vessels in the exposed membranes (their Figure 1(B) effectively illustrates this). However, extension of the incision may tear the vessels even without direct injury to them [3]. Furthermore, cutting only the uterine wall throughout the entire incision plane is not easy for a relatively inexperienced physician. In our opinion, uterine incision should be performed at the uterine part beneath where no aberrant vessels are present. Previous researchers [4] also state this view: “the addition of 3D power Doppler angiography made it possible to precisely map out the course of the fetal vessels to make the appropriate surgical incision into the uterus”. Oyelese and Smulian [5] also emphasized the importance of deciding the uterine incision site in this condition. Irrespective of the usage of 3D power Doppler, mapping of the aberrant vessels and thereby avoiding incising the uterine wall with aberrant vessels beneath it may be safer. In Bręborowicz et al.’s particular case, there may have been no adequate incision site and they may have been confident of their skills. Regardless of this, we should be aware that injuring aberrant vessels during cesarean section may cause significant fetal blood loss. We state this because their Figure 1(B) is so impressive.

Declaration of interest

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of this article.