Abstract
As part of Assisted Reproductive Technologies (ART), the advent of embryo freezing lowered the number of embryos transferred, decreasing multiple births without jeopardizing pregnancy rates. Using vitrification technology, 90% of embryos survive after thawing, producing clinical pregnancy rates similar to those of fresh embryos (41.6%y 44.3% respectively). Furthermore, cumulative pregnancy rates, obtained after transferring fresh plus frozen/thawed embryos, can reach 70%. Frozen embryo transfers (FET) are reported by six of seven institutions, which are part of the Chilean ART registry, and altogether constitute 22.8% of all ART procedures. Increasing use of cryopreservation lowered overall multiple gestations from 33% in 1995 to 23% in 2011, reducing pre term births and perinatal mortality. For many people, embryo freezing generates ethical dilemmas, due to the potential risks to which embryos are exposed, and the uncontrolled accumulation and disposal of human embryos. Scientific evidence today shows that frozen/thawed embryos are not exposed to disproportionate risks, and by hindering its use, both women and their children are exposed to the risks of multiple gestation, repeated cycles of ovarian hormonal stimulation or the impossibility to afford repeated ART cycles. In this article, we provide biomedical, as well as ethical, arguments to sustain that embryo cryopreservation is not only justified but fundamental when offering infertility treatment with ART.
Highlights
As part of Assisted Reproductive Technologies (ART), the advent of embryo freezing lowered the number of embryos transferred, decreasing multiple births without jeopardizing pregnancy rates
Scientific evidence today shows that frozen/thawed embryos are not exposed to disproportionate risks, and by hindering its use, both women and their children are exposed to the risks of multiple gestation, repeated cycles of ovarian hormonal stimulation or the impossibility to afford repeated ART cycles
We provide biomedical, as well as ethical, arguments to sustain that embryo cryopreservation is justified but fundamental when offering infertility treatment with ART. (Rev Med Chile 2014; 142: 896-902) Key words: Cryopreservation; Embryo dispositions; Embryo research; Legislation; Moral obligations; Reproductive techniques
Summary
As part of Assisted Reproductive Technologies (ART), the advent of embryo freezing lowered the number of embryos transferred, decreasing multiple births without jeopardizing pregnancy rates. Estos avances lograron tasas de sobrevida embrionaria al descongelar entre 90 y 97%, cuando los embriones se criopreservan en estado de blastocistos, es decir, al quinto día del desarrollo in vitro[3]. La Figura 1 muestra la dinámica del desarrollo y muerte embrionaria pre-implantacional en más de 500 embriones cultivados in vitro en el Programa de Reproducción Asistida de Clínica Las Condes. La comunidad médica respondió a este dilema con la criopreservación embrionaria, que permite, entre otras cosas: a) estimular hormonalmente a la mujer con el objeto de obtener varios óvulos; b) fecundar los óvulos maduros; c) esperar a que ocurran las muertes embrionarias que deben ocurrir y si uno o más embriones llegan al estado de blastocisto, transferir a la mujer uno o máximo dos embriones, y d) si hay embriones remanentes, vitrificarlos para una futura transferencia
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