ABSTRACT
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.