After three days of fertilization, when the embryo develops 8 to 10 cells, it is considered a healthy embryo. However, the real marvel unfolds on day 5 or 6 of fertilization when the blastocyst embryo emerges, revealing a higher number of cells. This crucial stage sets the foundation for the embryo’s future, designating specific cells for different roles – the inner group becoming the embryo itself, and the outer group forming the protective cells. The trophectoderm, the surface cells, are destined to become the placenta, while the inner cell mass transforms into the fetus. A healthy blastocyst, ideally, should hatch from its shell (zona pellucida) by the end of six days or earlier, ready to embark on the journey of implantation within the lining of the uterus.
The Role of Expertise and Technology:
The success of fertilization, particularly in developing blastocyst embryos, is intricately linked to the proficiency of the embryology team and the technological capabilities of the laboratory. It is a collaborative dance where the hands of skilled professionals and the precision of advanced equipment harmonize to create the optimal environment for embryo development.
The Advantage of Blastocyst Transfer:
Across clinics globally, the practice of transferring blastocyst embryos has become commonplace. Research suggests that such transfers yield higher implantation rates compared to transferring embryos on day three. If you find yourself with embryos frozen on day three, facing the decision of when to transfer, two options unfold. One can either opt for a day three transfer or thaw the embryos, allowing them to reach the blastocyst stage on day five or six. While waiting for blastocyst development increases the likelihood of successful implantation, it does carry the risk of potential embryo loss during the critical transition from day three to day 5-6. It is a delicate balance, and decisions should align with the individual circumstances and goals of the intended parents.
Clinics commonly use the quick freezing of embryos called the vitrification method. The media used is also universal, and if the embryos are shipped outside the clinic where they were created, the receiving clinic will thaw the embryos with available media. If the embryos were frozen using a method other than vitrification (e.g., slow freezing), it is suggested to inform the receiving clinic before shipment, as they need to organize thawing media for these embryos. Most clinics do not store slow freezing embryo thawing media, as they have limited validity and are not commonly used or needed.
