Antenatal Diagnosis of Type-3 Vasa Previa

INTRODUCTION

Type-3 vasa previa is a new and rare phenotype of vasa previa.¹ Some branches of the fetal vessel go out of the placental surface and subsequently come back to the placental cotyledons. In this report, we present a case of type-3 vasa previa diagnosed at 32 weeks of gestation.

CASE DESCRIPTION

A 38-year-old pregnant Japanese woman, G (4), P (2), was re-examined using transvaginal two-dimensional (2D) sonography and color Doppler at 32 weeks of gestation due to suspected vasa previa based on a previous routine obstetric examination at 31 weeks and 4 days of gestation using color Doppler. In this case, partial placenta previa was suspected at 18 weeks of gestation. Transvaginal 2D sonography clearly showed one small tubular structure near the internal cervical os (Fig. 1). Color Doppler revealed that this structure was a small velamentous blood vessel near the internal cervical os (Fig. 2). Pulsed Doppler ultrasound revealed that this vessel was an artery with arterial blood flow consistent with the fetal heart rate (Fig. 3).

At 37 weeks and 6 days of gestation, a scheduled cesarean section was performed, resulting in a viable, single female newborn weighing 2,726 g, with a height of 49 cm. The Apgar scores were 9 (1 minute) and 9 (5 minutes), and the umbilical artery blood pH was 7.34. Placental examination showed peripheral insertion of the umbilical cord with one aberrant small vessel (Fig. 4). The mother and neonate followed a favorable course after delivery.

DISCUSSION

Catanzarite et al.² classified vasa previa into two types: type I, a single placental lobe with a velamentous cord insertion, and type II, the vessels over the cervix between lobes of a multilobed placenta. Suekane et al.¹ reported a third phenotype of vasa previa, namely type-III vasa previa. In this type, some branches go out of the placental surface and subsequently come back to the placental cotyledons. In our case, peripheral insertion of the umbilical cord with one aberrant vessel was clearly identified using transvaginal 2D sonography and color Doppler. Macroscopic examination showed peripheral insertion of the umbilical cord with one small aberrant vessel. Therefore, cross-examination using transvaginal 2D sonography and color Doppler around the internal cervical os should be mandatory for the accurate prenatal diagnosis of vasa previa to prevent the perinatal fetal loss, especially in cases with placenta previa and low-implanted placenta at around 20 weeks of gestation.³

ORCID

Toshiyuki Hata https://orcid.org/0000-0002-8835-8554

REFERENCES

1. Suekane T, Tachibana D, Pooh RK, et al. Type-3 vasa previa: normal umbilical cord insertion cannot exclude vasa previa in cases with abnormal placental location. Ultrasound Obstet Gynecol 2020;55(4):556–557. DOI: 10.1002/uog.20347.

2. Catanzarite V, Maida C, Thomas W, et al. Prenatal sonographic diagnosis of vasa previa: ultrasound findings and obstetric outcome in ten cases. Ultrasound Obstet Gynecol 2001;18(2):109–115. DOI: 10.1046/j.1469-0705.2001.00448.x.

3. Hata T, Takayoshi R, Koyanagi A, et al. Vasa previa depicted by simple clear flow. Donald School J Ultrasound Obstet Gynecol 2020;14(2):161–163. DOI: 10.5005/jp-journals-10009-1628.