Effects of euploid blastocyst morphological development on reproductive outcomes

Blastocyst culture and transplantation have now been widely used in most reproductive centers. Our aim was to explore the effects of euploid blastocyst morphological development on the reproductive outcomes of frozen-thawed euploid blastocysts on the fifth day or sixth day. The retrospective analysis included the clinical data of 849 patients who underwent euploid blastocyst transplantation between January 2014 and January 2018. The patients were divided into well-developed blastocysts (BB) or poorly developed blastocysts (BC, CB) groups according to blastocyst morphology grade. The intracytoplasmic sperm injection (ICSI) was carried out on the day of egg retrieval. Morphological evaluation of the resulting blastocysts was performed on Day5 or Day6 of in vitro culture. The pregnancy rate, cumulative pregnancy rate, live birth rate and cumulative live birth rate were the highest in the BB group (P ≤ 0.001). In addition, not only the pregnancy rate of CB group Day5 was lower than that of the BB (P = 0.005) and BC (P = 0.042) groups, but the live birth rate in CB group was lower than BB (P = 0.001) and BC (P = 0.007) groups. However, there was no difference in miscarriage rate among the three groups (P = 0.154). Furthermore, the miscarriage rate of BB (P = 0.048) and BC (P = 0.019) groups at the Day5 cycle was lower than the Day6 cycle. Blastocyst morphological development has positive effects on pregnancy rate and live birth rate, but has no effect on miscarriage rate.