Ischiopagus Conjoined Twins with Dividing Membrane and Two Yolk Sacs at 9 Weeks of Gestation: HDlive Silhouette Findings

INTRODUCTION

Conjoined twins are very rare, and only 12% are ischiopagus conjoined twins.¹ There have been only two reports on conventional three-dimensional (3D) ultrasound diagnosis of ischiopagus conjoined twins.^2,3 However, the image quality of 3D ultrasound in these studies was poor.

HDlive Silhouette generates a holography-like image of the fetus and placenta.^4–6 In the current study, we present a case of ischiopagus conjoined twins with a dividing membrane and two yolk sacs using this technique at 9 weeks and 1 day of gestation.

CASE DESCRIPTION

A 33-year-old pregnant Japanese woman, gravida 1, para 0, was referred to our ultrasound clinic at 9 weeks and 1 day of gestation due to suspected conjoined twins based on a previous routine obstetric examination at 8 weeks and 6 days of gestation. Two-dimensional (2D) sonography clearly showed ischiopagus conjoined twins with a dividing membrane (Fig. 1). Color Doppler revealed vascular communication between the conjoined twins in the pubic area and one umbilical cord (Fig. 2). HDlive Silhouette (Voluson E10 BT20, GE Healthcare Japan, Tokyo, Japan) clearly depicted ischiopagus conjoined twins with two yolk sacs (Fig. 3). After counseling, the parents opted to terminate the pregnancy. A final diagnosis could not be made because the embryo was destroyed during the evacuation procedure.

DISCUSSION

In our case, the presence of conjoined twins was suspected at 8 weeks of gestation, and the diagnosis of ischiopagus conjoined twins was made at 9 weeks using 2D sonography, color Doppler, and HDlive Silhouette. HDlive Silhouette clearly showed the connecting part in the pubic area between the two embryos and two yolk sacs. Moreover, a dividing membrane was evident by 2D sonography. Murakoshi et al.⁷ reported that monochorionic monoamniotic twin pregnancies with two yolk sacs may not be rare. As a possible explanation for two yolk sacs, Chmait et al.⁸ suggested spontaneous rupture of the dividing membrane in monochorionic diamniotic twins or the creation of an incomplete dividing membrane in monochorionic monoamniotic twins. Therefore, spontaneous rupture of the dividing membrane in monochorionic diamniotic twins may have occurred in our ischiopagus conjoined twins. To the best of our knowledge, this is the first reported case of ischiopagus conjoined twins with a dividing membrane and two yolk sacs described early in the first trimester of pregnancy. HDlive Silhouette may provide additional information for the prenatal diagnosis and pathogenesis of conjoined twins early in the first trimester of pregnancy.

REFERENCES

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