Embryo quality at the early stages of development and its relation to the evolution to the blastocyst stage

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To analyze the relation of embryo quality at the early stages of development (day 2 and 3 of development) and the evolution to the blastocyst stage. Retrospective study. Analysis of 229 patients (545 embryos) aged less than 38 years (average: 33), undergoing IVF (In vitro fertilization). It was compared on the second (D2) and third day (D3) of culture, the number of good and poor quality embryos, which became blastocysts. The same comparison was made considering only the embryos that achieved the blastocyst stage at day 5 (D5). It was also compared at D2 and D3, the number of good embryos that formed blastocyst at D5 and D6. It was considered as good quality embryos those that had two to four cells, and less than 20% of fragmentation on D2 and had six to eight cells and less than 20% of fragmentation on D3. Embryos that did not meet this classification were considered poor quality embryos. Statistical analysis was performed using the Student's t-test followed by Mann-Whitney. A greater (P < 0,001) number of embryos that presented good quality developed to blastocyst stage, compared to those with poor quality, both on D2 (N = 433 – 79% vs. N = 112 – 21%) and D3 (N = 366 – 67% vs. N = 179 – 33%). The same result was found for D5. Comparing good quality embryos, both at D2 and D3, that turned blastocysts at D5 and D6, the study revealed that the majority (P < 0,001) of embryos that showed good quality became blastocyst at D5 (D2: N=334, 77% – D5 vs N=101, 23% – D6; D3: N=287, 85% vs N=50, 15%). The majority of blastocysts formed came from embryos that presented good quality at D2 and D3. Embryos with good morphology originated more embryos at D5 than D6. The results indicate that morphological criteria for embryo evaluation are effective. The selection of good embryos based on morphology at the early stages of development helps to predict the formation of blastocyst.