Blastocyst culture and transplantation are considered the gold standard of the IVF cycle. Many fertility clinics prefer to transplant Blastocytes, the five to six days older embryo instead of transferring two to three days old embryos (‘cleavage stage’) in IVF and ICSI treatment process.
This conventional treatment approach is based on the transplantation of blastocytes, which are better-developed embryos that increase the chance of successful treatment outcomes by achieving pregnancy and live birth.
The conventional treatment process promotes blastocyst transfer due to a higher delivery rate than cleavage-stage transfers, though it increases pregnancy complications and twin birth risks. According to the latest Cochrane review reported in 2016, fresh cleavage-stage transfer provides 29% of live birth, whereas blastocyst transfer leads to 32% and 42% of live birth. This difference occurs because the selection of viable embryos is much easier in the blastocyst stage, as they are more ‘physiological’. Nowadays, clinician prefers to transplant a single embryo to avoid multiple births.
The research team worked for the Committee of Nordic ART and Safety and also agreed that blastocyst transplantation is the best available embryo transferring method in IVF and other ART treatments. But certain precaution needs to take for a better outcome and avoid complications. They preferred to use frozen blastocyst transfer instead of extended embryo culture to avoid adverse effects associated with this culture. However, ongoing research studies try to develop a new technique to avoid blastocyst transfer associated adverse effects.
But nowadays, clinicians are concerned that the extended culture of the embryo in the laboratory set-up to achieve the blastocyst stage may cause obstetric complications and increase perinatal risks. Some research studies have compared the outcome of blastocyte implantation with three-day-old embryo transplantation and natural conceptions. The study result found that transplanting blastocysts increase the risk of preterm delivery before 37 weeks. The Committee of Nordic ART and Safety also supported this finding.
The Committee of Nordic ART and Safety conduct a cohort study. In this study, 90,000 assisted reproductions are included. This study finding also reported that babies born through blastocyte transplantation have greater birth weight, length, and head circumference than normal due to large gestational age than cleavage-stage embryo transfer or normal conception. Research investigators also mentioned that the risk of preterm birth is increased due to blastocyte transplantation.
Furthermore, these research findings also compare the twin birth rate in both blastocyte transplantation and cleavage stage transplantation. The study findings showed that the rate of twin birth is increased with blastocyte transplantation.
The study investigator of this research explained that the exposure to environmental circumstances is increased with blastocyte transplantation in the case of in vitro fertilization treatment process. During this extended period, embryos are in contact with external potential stressors including temperature difference and oxygen concentration. Also, the preparation of culture media differs from blastocyte transplantation to cleavage stage transplantation. This culture content difference also influences the genetic expression of the embryo and also provides an impact on perinatal outcomes.