PMC9280862_01
Ultrasound image during the first trimester. At the 59th days of pregnancy, ultrasonography shows one gestational sac with three yolk sacs (A). At 13 0/7 weeks of gestation, fetuses (A-C) are separated by intertwin membranes (arrow).
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F1
Early ultrasonography indicated the diagnosis of monochorionic triamniotic triplet pregnancy at 13 0/7 weeks of gestation (Figure 1), the crown-rump length (CRL) was 73.6/67.4/72.3 mm and the nuchal translucency (NT) was 1.5/1.4/1.3 mm respectively.
Ultrasound image of the surviving twin after RFA (A). Ultrasound image of TTTS, the donor amnion (white hand) floating in the amniotic cavity (B).
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F2
Twenty-four days after RFA surgery, ultrasonography confirmed the diagnose of twin-twin transfusion syndrome (Figure 2) and discordant fetal sex in the two surviving fetuses.
(A,B) Indicate the genotypes of the female recipient twin and the male donor twin at different loci, respectively. Because both alleles were different, the twins were accepted as DZ. Gross placental specimen appearing of the reduced male fetus (C), the male donor twin (D) and the female recipient twin (E), separated by white line respectively. Histological examination of intertwin membrane between the reduced male fetus and the female recipient twin (F), the female recipient twin and the male donor twin (G), reveals MC component. The black arrow showing cytolysis of amniotic epithelial cells of the reduced male fetus.
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F3
The amniotic fluid for chromosome analysis revealed a normal male karyotype (46, XY) of the donor twin and normal female karyotype (46, XX) of the recipient twin, and short tandem repeat (STR) analysis revealed dizygotic twins (Figures 3A,B). Pathological examination confirmed the diagnose of monochorionic triamniotic pregnancy (Figures 3C-G).