In vitro fertilization (IVF) is a procedure performed to overcome female and male infertility. During oocyte aspiration, it can occur retrieval of mature oocytes, in metaphase II (MII), or meiotically immature, in metaphase I (MI). These can spontaneously mature in vitro for MII within a few hours. As women age, there is a decrease in the quantity and quality of oocytes collected. The increase in pregnancy rate is directly related to the number of blastocysts obtained in the IVF cycle. Objective: To evaluate blastocysts formation rates from MI oocytes. Methods: Cross-sectional study. A total of 164 patients were selected to perform IVF at the Pronatus Clinic from January 2013 to December 2016. Results: In total, 1467 oocytes were fertilized by ICSI, which 1153 were in the MII stage and 314 in the MI. Considering these 314 MI, 201 matured in vitro for MII (MI-MII) and 113 remained in the MI stage after 3 hours in culture. The mean age of the patients was 35.6 years. In vitro maturation rate was 64.01%. Fertilization rate in MI oocytes was the lowest (31.9%), while MII oocytes had the best rate (79.1%). The comparison of fertilization rate showed that MI oocytes have 88% lower chance of forming embryo with 2 pronuclei than MII oocytes (p<0.001). It was noted that embryos from MI stage have the highest incidence of multinucleation and are 2.63 times more risk to have abnormalities of cell division in relation to MII (p=0.008). The blastocyst formation rate was higher in embryos from MII oocytes (36.4%), MI-MII oocytes rate was 11.4% and embryos from MI oocytes was 0.8%. The risk of MI oocytes not forming a blastocyst is 99% in relation to the MII (p<0.001). When correlating age with both oocyte retrieval and blastocyst formation, it was observed that the quantity of MII oocytes decreased with increasing age (p=0.002) and there was a decrease in blastocysts formation from these oocytes in patients over 40 years (p=0.03). Conclusion: The use of MI oocytes in IVF should be discouraged, since they have low potential for embryonic development and form embryos of low quality, with a rate of blastocyst formation of less than 1%. However, the use of in vitro matured MI for MII oocytes can be stimulated in IVF cycles, as an alternative to low obtaining MII oocytes in elderly women.
|
