Determining the cause of intrauterine fetal death in monochorionic twins: A case report

Abstract

Background: Determining the cause of intrauterine fetal death is essential for patients to manage their next pregnancy. However, in the majority of cases of fetal death, the cause remains unexplained despite comprehensive evaluation, especially in the cases of twins. Among twin pregnancies, conditions of monochorionic twinning, commonly regarded as monozygotic, are more complicated than dichorionic ones.

Case summary: We systematically evaluated the cause of fetal death for a Han Chinese woman with monochorionic twinning following in vitro fertilization/embryo transfer. Discrepant karyotypes were unexpectedly discovered between the twins. One fetus had an aneuploid male karyotype (46, XY), dup (9) (p24.3-q13), and the other had a normal female karyotype (46, XX). We considered that the male died of aberration of chromosome 9 and the female died of subsequent acute exsanguination through vascular anastomosis.

Conclusion: This study demonstrated the importance of recognizing the presence of monochorionic dizygotic twinning and the challenges of clinical management for twins following in vitro fertilization/double embryo transfer.

Keywords: case report; double-embryo transfer; fetal death; monochorionic dizygotic (MCDZ) twins; partial trisomy 9; vascular anastomoses.

FIGURE 1

Ultrasound images revealing the monochorionic twins and twin A’s nuchal cystic hygromas and twin B’s normal NT. (A) Two yolk sacs within a single gestational sac at 6⁺² weeks. The arrow indicates two yolk sacs. (B) The monochorionic diamnitic twins with a separating membrane of T sign at 10⁺³ weeks. The arrow indicates the distinct T sign of the separating membrane between the twins. (C) Nuchal cystic hygromas of twin A at 12⁺³ weeks. The arrows indicate the nuchal cystic hygromas of twin A from longitudinal section and transverse section. (D) The normal NT of twin B at 12⁺³ weeks. NT, nuchal translucency.

FIGURE 2

Histopathology images showing the examination of two fetuses and the placenta. (A) Macroscopic examination of the twins. Twin A (right), severe cystic hygroma and generalized hydropic foetalis, appearing decaying tissue. Twin B (left), unremarkable macroscopic abnormality. (B) The monochorionic diamniotic placenta of the twins. The placental septum indicates two amniotic sacs beside thin membranes. (C) Microscopic histopathological examination of the placental section (H&E staining, 10×).

FIGURE 3

Schematic drawing of two types of embryonic development with monochorionic diamniotic twins after double-embryo transfer. (Above) The formation of monochorionic monozygotic twins in common cases. (Below) The formation of monochorionic dizygotic twins in this case. MZ, monozygotic; MC, monochorionic; DZ, dizygotic; DiMo, diamniotic; ICM, inner cell mass; D, day. (A) Enlarged view illustrates the cause of death of twin A, the duplicated segment of chromosome 9; (B) enlarged view illustrates the cause of death of twin B, the vascular anastomoses between the twins.