Antenatal Diagnosis of Dizygotic, Monochorionic Twins Following IVF/ICSI

Abstract

Monochorionic twins are usually monozygotic and thus usually have the same sex. A case of monochorionic diamniotic twins following IVF/ICSI and laser treatment of the zona pellucida (“assisted hatching”) is presented in which partial embryo amalgamation appears to have occurred. Discordant sex between the twins was suspected on detailed antenatal ultrasound at 13 + 3 weeks gestation and was confirmed on subsequent examinations. The sexual phenotype at birth was female for one twin and male for the other. Placental histology confirmed the monochorionic, diamniotic situation. Cytogenetic analysis of both twins was carried out postpartum on various tissues. On karyotyping of blood lymphocytes the male and female twins each had one mosaic of male and female cells. Oral mucosal cells showed normal male and female karyotypes respectively. Analysis of urothelium showed a normal result for the male infant, and a weak gonosomal mosaic with an XX and XY constellation for the female infant. At least for blood lymphocytes, a diagnosis of chimerism was proven.

Zusammenfassung

Üblicherweise sind monochoriale Zwillingsschwangerschaften monozygot und weisen dasselbe Geschlecht auf. Im vorliegenden Fall war nach IVF/ICSI und Laserbehandlung der Zona pellucida („assisted hatching“) eine monochoriale, diamniote Geminigravidität eingetreten, bei der es wohl zu einer partiellen Verschmelzung der Embryonen kam. Pränatal wurde in der 13 + 3 SSW im Rahmen einer detaillierten Ultraschalldiagnostik der Verdacht auf eine Diskrepanz der Geschlechter der Gemini gestellt, der sich in den Folgeuntersuchungen bestätigte. Post partum war das phänotypische Geschlecht des einen Zwillings weiblich und des anderen männlich. Die Histologie der Plazenta bestätigte die monochorialen, diamnioten Eihautverhältnisse. Postnatal erfolgte die zytogenetische Analyse der Zwillinge in verschiedenen Geweben. Die Karyotypisierung an Blutlymphozyten ergab für den weiblichen und männlichen Zwilling jeweils ein Mosaik aus männlichen und weiblichen Zellen. In den Mundschleimhautzellen zeigte sich für beide Neugeborene ein unauffälliger männlicher bzw. weiblicher Karyotyp. Die Diagnostik an Urothelzellen war für das männliche Neugeborene ebenfalls unauffällig und zeigte für das weibliche Neugeborene ein schwaches gonosomales Mosaik mit XX- und XY-Konstellation. Zumindest für Blutlymphozyten konnte die Diagnose der Chimären bewiesen werden.

Key words

sex discordance - gemini - ART - sonography

Schlüsselwörter

Chimären - Geschlechtsdiskrepanz - Geminigravidität - ICSI - Ultraschalldiagnostik

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