Zusammenfassung
Aufgrund der verbesserten Kulturtechnik durch den Einsatz sequenzieller Medien ist es heute möglich, Embryonen 5 Tage nach Eizellgewinnung im Blastozystenstadium zu transferieren, was die Selektion von Embryonen mit einer guten Implantationschance erlaubt. In Deutschland muss die Auswahl der zu transferierenden Embryonen bereits im Pronukleusstadium getroffen werden. Das Deutsche Embryonenschutzgesetz verbietet die Kultur von mehr als 3 Embryonen. Es dürfen nur so viele Embryonen kultiviert werden, wie auch wieder übertragen werden sollen. Das bedeutet, dass bereits im Pronukleusstadium die Embryonen identifiziert werden müssen, die ein hohes Potenzial für eine erfolgreiche Implantation besitzen. Da dies nur unzureichend möglich ist, ist in Deutschland keine höhere Implantationsrate als 10–15% pro Embryo zu erwarten. Die Implantationsraten nach Blastozystenkultur erreichen dagegen bis zu 50%. Eine hohe Schwangerschaftsrate kann jedoch nur erzielt werden, wenn mehrere Oozyten bzw. Zygoten vorhanden sind, aus denen in einem späteren Entwicklungsstadium eine Selektion möglich ist. Durch das hohe Implantationspotenzial von Blastozysten werden weniger Embryonen für den Transfer benötigt, was die Inzidenz von Mehrlingsschwangerschaften erniedrigt. Unter deutschen Bedingungen vermag die Blastozystenkultur im Vergleich mit der konventionellen Kultur bis zum Tag 2 oder 3 die Schwangerschaftszahlen nicht zu steigern.
Abstract
Due to improvements in human embryo culture in recent years, it is now possible to transfer embryos 5 days after oocyte retrieval at the blastocyst stage allowing the selection of the embryo with the best implantation potential. In Germany the selection of embryos has to be performed already at the pronuclear stage. The German Embryo Protection Law prohibits the culture of more than three embryos. Only as many zygotes as will be presumably transferred may be cultured. Therefore, the selection of the embryo with the best developmental potential has to be done at the pronuclear stage. Thus, the implantation rate per cleavage stage of embryo transferred has not increased beyond 10–15%, and the implantation rates after blastocyst culture are reported to range up to 50%. High pregnancy rates, however, can only be achieved when a cohort of several oocytes or zygotes is available and selection can be done during the embryo culture and at the blastocyst stage. The high implantation potential of blastocysts means that fewer embryos are required for transfer to achieve a clinical pregnancy than for the transfer of cleavage stage embryos with a reduction of the incidence of multiple pregnancies. Under the current legal conditions in Germany, blastocyst culture cannot improve pregnancy rates.
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Zollner, U., Zollner, KP. & Steck, T. Blastozystenkultur unter den Bedingungen des Deutschen Embryonenschutzgesetzes. Gynäkologische Endokrinologie 1, 176–182 (2003). https://doi.org/10.1007/s10304-003-0042-5
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DOI: https://doi.org/10.1007/s10304-003-0042-5