Antenatal three-dimensional sonographic features of placental shelf.

Abstract

The sonographic appearance of tissue contiguous with the edge of the placenta that protrudes into the amniotic cavity is called a placental shelf, and this shelf is considered to represent a circumvallate placenta [1, 2]. A circumvallate placenta in the third trimester may cause placental abruption, preterm delivery, fetal growth restriction, and perinatal death [3]. However, Shen et al. [2] reported that an early second-trimester placental shelf appears to be a common, benign, and transient sonographic finding, and never persists to the third trimester. We describe a case of an early second-trimester placental shelf diagnosed by conventional two-dimensional (2D) and three-dimensional (3D) ultrasound, but a partially circumvallate placenta was confirmed after delivery in the present case. A 35-year-old woman, gravida 4, para 3, was referred to our ultrasonography clinic because of suspected amniotic band syndrome at 18 weeks and 2 days of gestation. Conventional 2D ultrasound (Voluson E-8, General Electric Medical Systems, Kretztechnik, Zipf, Austria; curvilineararray transabdominal transducer, 2–5 MHz) revealed typical findings of a placental shelf (Fig. 1). 3D ultrasound (Voluson E-8, General Electric Medical Systems, Kretztechnik, Zipf, Austria; curvilinear-array transabdominal transducer, 2–5 MHz) clearly depicted its features, i.e., a smooth, round, and thick free edge with a triangular shape (Fig. 2). The placental shelf was not attached to any fetal parts, and there was no fetal abnormality. The shelf could not be detected 3 weeks later. A healthy male infant weighing 2,604 g was delivered by elective cesarean section at 37 weeks and 4 days of gestation, with Apgar scores of 8 and 9 at 1 and 5 min, respectively. The placental weight was 480 g, and the macroscopic findings revealed a partially circumvallate placenta (Fig. 3). There have been some reports of antenatal detection of a placental shelf using conventional 2D ultrasound [1, 2]. However, visualization of the continuity and extension of the placental shelf was not easily accomplished with conventional 2D ultrasound. There has been only one reported case of a placental shelf diagnosed by prenatal 3D ultrasound [2]. As shown in the present and previous reports, more detailed information on the placental shelf was obtained by means of 3D ultrasound. In particular, the special relationship between the placental shelf and fetus visualized by 3D surface-rendered display was more readily discernible as compared with conventional 2D ultrasound. 3D ultrasound has the potential to supplement conventional 2D ultrasound in diagnosing a placental shelf. Moreover, 3D sonographic images provide entirely new visual experiences for examiners and couples owing to the near-photographic depiction of the placental shelf and fetal conditions in utero. Shen et al. [2] detected 17 placental shelves (11.2%) in 152 consecutive anomaly scans performed between 13 and 16 weeks of gestation. In their study group, early secondtrimester placental shelves rarely persisted to mid-gestation, and never to the third trimester. All placentas with early second-trimester placental shelves were normal, and there were no placenta-related perinatal problems [2]. In T. Hata (&) T. Fujiwara M. Ishibashi E. Kuwamura C. Tenkumo Department of Perinatology and Gynecology, Kagawa University School of Medicine, 1750-1 Ikenobe, Miki, Kagawa 761-0793, Japan e-mail: toshi28@med.kagawa-u.ac.jp