JBRA Assist. Reprod. 2011;15(3):32-33
ARTIGO ORIGINAL
doi: 10.5935/1518-0557.2011.15.3.08
Grupo PRANOR de Reproducción Asistida, Lima, Perú
SUMMARY
Introduction-objective: The human embryo culture is performed in incubators with an atmosphere of ~20% oxygen, a different situation from the human tube, estimated at 5%. Currently, there are trigas incubators where the embryos can be grown in this condition.The aim of this study was to compare pregnancy and implantation rates in oocyte donation cycles, when using incubators with ~ 20% oxygen versus incubators with 5% oxygen.
Material and methods- we designed a prospective randomized study with 50 cycles per arm. Blastulation rate, proportion of vitrified embryos and the quality of the inner cell mass of the embryo were also compared.
Results- The pregnancy rate was similar in both conditions, 55.3% for 5% oxygen and 54.6% for ~ 20% oxygen. The implantation rate was 36.8% for ~ 20% and 41.8% for 5%.Patients using trigas incubators had a higher rate of embryo freezing: 30.8% versus 19.2% (p <0.0003) of patients using conventional incubators. This means that 55.4% of embryos developed in trigas was of good quality, versus only 41.8% in conventional (p<0.0002).
Conclusionwe suggest that trigas incubators are more efficient and allow the development of higher quality embryos compared to conventional incubators. We expect that will be reflected in the cumulative pregnancy rate.
Keywords: blastocyst culture, oxygen tension
RESUMO
Introdução-objetivo- O cultivo de embriões é realizado em incubadoras com uma atmosfera de oxigênio de ~20%, uma situação diferente das trompas uterinas, onde se estima em 5%. Atualmente, existem incubadoras trigas, que podem cultivar os embriões nestas condições. Comparamos as taxas de gestação e implantação em ciclos de doação de óvulos, com incubadoras com oxigênio ~ 20% versus incubadoras com 5% de oxigênio.
Material e método- Estudo prospectivo e randomizado com 50 ciclos por grupo. Também comparamos a taxa de blastulação, a proporção de embriões vitrificados e a qualidade da massa celular interna do embrião.
Resultados- A taxa de gestação foi semelhante em ambas as condições, de 55,3% para 5% e 54,6% para ~ 20%. A taxa de implantação foi de 36,8% para ~ 20% e 41,8% para 5%.Pacientes em uso de incubadoras de trigas apresentaram uma maior taxa de congelamento de embriões, 30,8% versus 19,2% (p <0,0003) do que pacientes em uso de incubadoras convencionais. Isso fez com que 55,4% dos embriões se desenvolveram com boa qualidade em trigas, versus 41,8% no convencional (p <0,0002).
Conclusão- Sugerimos que uma incubadora trigas é mais eficiente para permitir o desenvolvimento de embriões de melhor alta qualidade, que será refletido na taxa de gravidez cumulativa.
Palavras-chave: cultura de blastocisto, tensão de oxigênio
RESUMEN
Introducción-objetivo- El cultivo de embriones humanos se realiza en incubadoras que tienen una atmosfera de ~20% de oxígeno, situación diferente a la trompa materna, que se estima en 5%. Actualmente, existen incubadoras trigas, donde se puede cultivar en esta condición. Comparamos las tasas de embarazo e implantación en ciclos de ovodonación, cuando se utilizaba incubadoras con ~20 % de oxigeno versus incubadoras con 5% de oxígeno.
Materiales e método- se diseñó un estudio prospectivo al azar, con 50 ciclos por brazo. Se comparó además, tasa de blastulación, proporción de embriones vitrificados y la calidad de la masa celular interna del embrión.
Resultados- La tasa de embarazo fue semejante en ambas condiciones, 55.3% para 5% y 54.6% para ~20%. La tasa de implantación fue 36.8 % para ~20 % y 41.8 % para 5%.Pacientes que utilizaron las incubadoras trigas, tuvieron una mayor tasa de congelación de embriones, 30.8 % versus 19.2 % (p < 0.0003) de las pacientes que usaron las incubadoras convencionales. Esto hace que un 55.4 % de los embriones desarrollados en trigas fuera de buena calidad, versus un 41.8 % en convencional (p<0.0002).
Conclusion- se sugiere una mayor eficiencia de las incubadoras trigas, al permitir el desarrollo de un mayor número de embriones de óptima calidad, lo cual se verá reflejado en la tasa de embarazo acumulativa.
Palabras clave: cultivo a blastocisto, tensión oxigeno
INTRODUCTION
Human embryo culture is performed in incubators with an atmosphere of approximately 20% oxygen, a situation different from the tube, which is estimated at 5%. Currently, there are trigas incubators, which can be grown in this condition of hypoxia, similar to the maternal condition. These incubators are also heat stable and open recovery is much faster, lasting between 1 and 10 minutes instead of 4 hours.
Trigas incubators are easy to clean and its microenvironment is insulated from changes in the environment, as the gases come in a ready-mix, directly to the hatchery tank.
Several authors agree that the presence of oxygen is detrimental to embryonic development despite the fact that you can obtain blastocysts and have an apparently normal morphology. It has been reported that culture of embryos in low oxygen concentrations does not have an adverse effect on fertilization and early development of embryos (Dumoulin et al, 1999; Kovacic & Vlaisavljević, 2008). However, it has shown differences in the development of inner cell mass of the blastocyst which will develop into an embryo (Bavister, 2004; Kea et al, 2007). This is reflected in a higher rate of implantation and live birth (Meintjes et al., 2009).
A retrospective analysis comparing the oxygen conditions on the results of our assisted reproduction program, suggested best results when the gametes and embryos were cultured in trigas incubators. Therefore, we designed a prospective, randomized study within an egg donation program, growing oocytes and embryos of 50 recipients in the conventional incubator (~ 20% O2) and the other 50 recipients in incubators with (5% O2). The aim of this work was to analize the different outcome obtained when using 5% oxygen versus ~20%. . We compared the embryonic development and fertilization, pregnancy and implantation rates.
MATERIAL AND METHODS
A randomized prospective study was designed in an oocyte donation program, growing oocytes and embryos from 100 cycles of recipients in the two study conditions, placing 50 cycles for each arm.
The day before aspiration, when the culture plates were prepared for the following morning, the recipients were randomly distributed in the two different types of incubators: 20% oxygen (standard) or 5% oxygen (trigas). Cycles were excluded for medical indications, which led to change the date of transfer or send the case to genetic diagnosis. Gametes and embryos were cultured in Global family media, until day 5 of development. Embryo quality was evaluated and blastocysts were graded, according to protocols already described (Sepulveda et al., 2009). A maximum of two embryos was transferred to each patient. The preparation of the endometrium in patients receiving embryos was performed by oral administration of estradiol valerianate (Progynova ®, Schering) with 2 to 6 mg per day, in ascending order on day 2 or 3 of the cycle. Receptors required an endometrial thickness of 8 mm minimum before receiving progesterone. They received 600 mg micronized progesterone (Geslutin ®, Tecnofarma) daily by vaginal route, starting on the day of follicular puncture for oocyte donor up to the day of the pregnancy test (quantification of the beta subunit of hCG). If the pregnancy test was positive, progesterone supplementation continued for 3 months.
RESULTS AND DISCUSSION
Groups analyzed were similar as described in Table 1, both for the age of the donor, the recipient’s age and the number of embryos transferred.
The fertilization rate for the trigas group was 72.4% compared to 71.7% (Table 2) for the standard group. Nor was there any difference in pregnancy rates which were 55.3% and 54.6%, respectively (Table 3). There is an upward trend in the rate of multiple pregnancies, 46.2% versus 29.2%, but is not significant (Table 3). Kovacic et al. (2010) found no differences in pregnancy rates in ICSI cycles. However, if they compared the cumulative pregnancy rate, it was higher in trigas incubators.
We conclude that there was no difference in pregnancy rate since, in all cases, there were many embryos from which to perform a selection, only the 2 best being transferred. The implantation rate in the trigas group was 41.8% while the standard group was 36.8% (Table 4). Again, a trend in favor of trigas was observed but it is not significant. Blastulation rate was 46.2% in 5% oxygen and 40.0% in ~ 20% oxygen (Table 5). If we analyze the quality of blastocysts, using as parameter the quality of inner cell mass (ICM), there is a significant difference in favor of low oxygen culture, where 46.8% of blastocysts showed a good quality MCI.
Since the data suggests, although it does not show, a better embryo quality, we analyzed the quality of the blastocysts and the number of good quality embryos produced in both conditions, adding the transferred embryos and vitrified embryos (Table 6). It is possible to see that there is a higher percentage of embryos frozen in the trigas group (30.8% vs 19.2%) and there is significant difference when comparing the proportion of good quality embryos.
CONCLUSION
Culture in low oxygen conditions would be favorable for embryonic development up to day 5. Although there is no significant difference in pregnancy and implantation rates, there was a higher number of blastocysts of good quality under these conditions, leading to a higher proportion of vitrified embryos, for a next cycle. This could be reflected in the cumulative pregnancy rate