Freeze-all en reproducción asistida

Los avances en los protocolos de vitrificación y los resultados obtenidos tras la transferencia de embriones congelados han dado lugar a una versión distinta de los ciclos estándar de reproducción asistida: los ciclos freeze-all. Independientemente de su uso frente a las indicaciones más comunes (progesterona elevada, riesgo de hiperestimulación, entre otros), este nuevo concepto hoy representa una práctica habitual en muchas clínicas siendo aplicado a todas las pacientes. En este artículo analizaremos los distintos factores que pudieron haber contribuido a este cambio de política y la evidencia científica en relación al tema. Basados en esta evidencia concluiremos si las clínicas deberían cambiar su forma de trabajo pasando de transferencias de embriones frescos a solo transferencia de embriones congelados o si deberíamos mantener el protocolo estándar.

Breakthroughs in vitrification protocols and the results obtained after frozen embryo transfer have resulted in a different version of the assisted reproduction standard cycles: the "freeze-all" cycles. Regardless of their use beyond the usual indications (elevated progesterone, risk of hyperstimulation, among others), this new concept currently represents a common practice in many institutions and is applied to all patients. In this article, we will discuss the various factors that may have contributed to this change in policy and the scientific evidence for this topic. Based on this evidence, we will conclude if clinics should change their way of working from fresh embryo transfers to only transfer frozen embryos, or if we should maintain the standard protocol.

Comparación de la tasa de embarazo con embriones desvitrificados transferidos por ciclo natural vs ciclo con preparación endometrial / Comparison of pregnancy rate for embryos transferred in natural cycle vs cycles with endometrial preparation

Resumen OBJETIVO: comparar la tasa de embarazo en ciclos de transferencia de embriones vitrificados versus ciclos naturales y con preparación endometrial. MATERIALES Y MÉTODOS: estudio comparativo, observacional y retrospectivo efectuado mediante la revisión de expedientes clínicos de procedimientos de fertilización in vitro efectuados entre enero de 2010 y diciembre de 2013. Los casos se dividieron en dos grupos: ciclo natural y preparación endometrial. Se analizaron las variables de edad, IMC, FSH, LH y estradiol al inicio del ciclo, progesterona el día del inicio del soporte lúteo, LH, y estradiol el día de transferencia, supervivencia embrionaria, número de embriones transferidos, calidad embrionaria y tasa de embarazo. Posterior al análisis principal los grupos se dividieron, nuevamente, de acuerdo con la calidad embrionaria. RESULTADOS: se revisaron 951 expedientes clínicos en los que se identificaron y analizaron 75 ciclos que reunieron los criterios de inclusión. No se encontraron diferencias en porcentaje de supervivencia embrionaria o número de embriones transferidos, ni en la tasa de embarazo entre los grupos. En el grupo con embriones de calidad regular se observó una diferencia significativa en las tasas de embarazo en transferencia en ciclo natural (15%) versus ciclos con preparación endometrial (33.3%) con una p significativa de 0.02. CONCLUSIONES: cuando la calidad embrionaria es regular, la tasa de embarazo es mayor que cuando la transferencia se efectúa en un ciclo con preparación endometrial.

Abstract OBJECTIVE: Compare pregnancy rates of thawed embryo transfer between natural cycle and endometrial preparation. MATERIALS AND METHODS: This is a comparative, retrospective, observational study. 951 medical files where reviewed in the from January 2010 to January 2014. 75 files met with the inclusion criteria. The cycle where divided into two groups. The first group, thawed embryos where transferred during a natural cycle without any hormonal therapy. The second group, thawed embryos where transferred to a prepared endometrium with GnRH agonist and exogenous estrogen. Two embryos where transferred if the patient had two or more viable thawed embryos and one in all other cases. Variables analyzed in both groups where, age, body mass index, FSH, LH, and estrogen at the beginning of the cycle, progesterone on the day of initiating luteal support, LH and estradiol the day of embryo transfer, post-thaw embryo survival rate, number of embryos transferred, embryo quality and pregnancy rate. Groups where then divided according to the embryo quality forming a good quality cohort and a regular quality cohort. In both groups transfers during a natural cycle where compared with embryo transfer to a prepared endometrium. RESULTS: There was no difference observed in embryo survival or number of embryos transferred between both groups. Embryo quality was statistically better in the group with prepared endometrium. There was no statistical significant difference in pregnancy rate between the two groups. In cycles with good quality embryos there was no statistical difference in pregnancy rate when embryos where transferred during a natural cycle versus those transferred to a prepared endometrium. In cycles with regular quality embryos there was a statistical significant difference in pregnancy rate. Pregnancy rate for thawed-embryo transfer during a natural cycle was 15% and 33.3% when the transfer was to a prepared endometrium (p = 0.02). CONCLUSION: Endometrial preparation increases de pregnancy rate when regular quality thawed-embryos are transferred.

Gonadotropin-Releasing Hormone (GnRH) Agonist Trigger in a GnRH Antagonist Protocol and Severe Ovarian Hyperstimulation Syndrome.

Aims: Ovarian hyperstimulation syndrome (OHSS) is an iatrogenic and potentially life-threatening complication of ovarian stimulation. The best strategy to prevent it is to use a gonadotropinreleasing hormone (GnRH) agonist (GnRHa) to trigger final oocyte maturation in a GnRH antagonist protocol, followed by cryopreservation of all oocytes/embryos (freeze-all strategy). The objective of this study is to describe two cases of a rare occurrence of severe OHSS following GnRHa trigger in a GnRH antagonist protocol and freeze-all strategy. Presentation of Case: Two patients (a 33-year-old patient, and a 31-year old patient) were submitted to in vitro fertilization (IVF). The ovarian stimulation started on day 2 of her menstrual cycle in a step-down GnRH antagonist protocol. The final oocyte maturation was induced with a bolus of 0.2 mg triptorelin in both cases. Due tothe risk of OHSS, all the embryos were cryopreserved and no embryo transfer was performed. In the case 1, two days after oocyte retrieval, the patient was seen at the emergency and was diagnosed with severe OHSS with bilateral pleural effusion. In the case 2, three days after oocyte retrieval, the patient was seen at the emergency unit and was diagnosed with severe OHSS. Both patients were managed in an intensive care unit. Conclusions: Unless the substitution of human chorionic gonadotropin (hCG) by GnRHa triggering in antagonist cycles is done in combination with no embryo transfer (which is the best form of OHSS prevention), and unless it virtually completely eliminates the onset of OHSS, this complication may still occur in certain groups of patients.