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Background: The occurrence of a discordant chromosomal abnormality in monozygotic twins is an extremely rare condition.
Case: We report the prenatal sonographic findings and cytogenetic studies in a monochorionic twin pregnancy discordant for severe fetal anomalies. Amniocentesis was normal for both twins. The pregnancy was managed conservatively, resulting in the delivery of discordant twins at 28 weeks. Cytogenetic analysis performed on cultured lymphocytes from peripheral blood revealed a mosaic 47XY+21 (in 2% of the cells)/46XY (in 98%) in the structurally normal twin, and a mosaic 47XY+21 (4%)/46XY (96%) for the abnormal twin. The abnormal neonate died shortly after delivery. The structurally normal twin survived without sequelae and had a normal karyotype 2 years later.
Conclusion: This report adds to the literature a case of a monochorionic twin pregnancy with a mosaic fetus who gives his co-twin trisomic cells through placental vascular anastomoses, this twin being a chimera, highlighting the necessity of performing molecular genetics with polymorphic DNA markers to differentiate chimerism from mosaicism and define the origin of cell lines.
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Ultrasound Obstet Gynecol
September 2025
Department of Clinical Genetics, Erasmus MC, University Medical Centre, Rotterdam, The Netherlands.
Objective: To evaluate the performance of non-invasive prenatal testing (NIPT) in vanishing-twin and multiple pregnancies.
Methods: This study was conducted as part of the TRIDENT-2 study, in which NIPT was offered as a first-tier screening test to women with a multiple pregnancy or vanishing-twin pregnancy between 1 June 2020 and 31 March 2023 in The Netherlands. Abnormal NIPT results were investigated by follow-up invasive prenatal testing and/or postnatal genetic testing.
Ultrasound Obstet Gynecol
September 2025
Child Neurology and Psychiatry Unit, Department of Paediatrics, Buzzi Children's Hospital, University of Milan, Milan, Italy.
Objective: Emerging evidence indicates that uncomplicated monochorionic diamniotic (MCDA) twins deviate physiologically from singletons, probably owing to adaptations to their unique intrauterine environment. However, their long-term neurodevelopmental outcomes remain poorly understood. Early identification of neurodevelopmental risks is critical to optimize neuroplasticity during key developmental periods.
View Article and Find Full Text PDFEarly Hum Dev
August 2025
Department of Pediatrics, Kitasato University, Kanagawa, Japan.
Background: Histological chorioamnionitis (HCAM) is associated with adverse neurodevelopmental outcomes; however, its role in extremely preterm twin pregnancies (<28 weeks of gestation), particularly in relation to chorionicity, is unclear.
Objective: To evaluate the association between HCAM severity and neurodevelopmental outcomes at 3 years old in extremely preterm twins, focusing on the modifying effect of chorionicity.
Methods: Utilizing data from the Neonatal Research Network of Japan (2004-2020), this retrospective cohort study included twins born at <28 weeks' gestation and birth weight < 1500 g.
PLoS One
September 2025
Department of Obstetrics and Gynecology, University of Washington, Seattle, Washington, United States of America.
Background: Maternal immunization relies on active transplacental transfer of immunoglobulin G. However, very little is known about the efficacy of maternal immunization in the setting of multiple gestation. We aimed to investigate transplacental transfer of maternal antibody in pregnancies with multiple gestation including mono- and dichorionic pregnancies by evaluating anti-Spike antibody transfer at delivery.
View Article and Find Full Text PDFInt J Surg Case Rep
August 2025
Department of Surgery, Faculty of Medicine University of Jaffna, Sri Lanka.
Introduction: Twin Reversed Arterial Perfusion (TRAP) sequence is an uncommon and severe complication of monochorionic twin pregnancies, characterized by an acardiac twin lacking a functional heart and a pump twin that maintains circulation for both.
Presentation Of Case: We report a case involving a 17-year-old primigravida diagnosed with a monochorionic diamniotic twin pregnancy at 8 weeks gestation. At 35 weeks, ultrasound revealed a teratogenous mass measuring 11 cm × 9.