Stims/Controlled Ovarian Hyperstimulation
The IVF process starts with the process of retrieving eggs in controlled ovarian hyperstimulation (stims) for the female or egg-having partner. In a regular ovulatory cycle, a sequence of hormonal changes leads to the maturation and release of a single mature egg. In an IVF stims cycle, medication is given for about 10-14 days to create several mature eggs at once. When the follicles have reached optimal size, the egg retrieval will be scheduled.
1a – Egg retrieval
Egg retrieval comes after the hyperstimulation process. The egg retrieval is a minimally invasive surgery performed with light sedation. The Reproductive Endocrinologist will retrieve the eggs from the ovaries using a needle through the vaginal wall. This is an ultrasound-guided procedure and takes about 20 minutes to complete. The eggs are taken back to the IVF laboratory.
1b – Sperm collection
The male partner will provide a sperm sample within 2 hours of the egg retrieval procedure. This can be done at the fertility clinic, at home on the day of the retrieval, or a frozen semen sample can be used.
2 – Fertilization
The embryologist will fertilize each egg separately with sperm from the partner or sperm donor. In order to reduce the risk of artifact DNA present within the embryo (which may make genetic testing more difficult), the majority of labs in the United States require the use of intracytoplasmic sperm injection (ICSI). ICSI is a procedure where a singular, good-quality sperm is injected directly into a mature egg.
3 – Embryo growth
Cells should multiply day by day to 2 cells, 4 cells, 8 cells, and by 5 days after fertilization, the embryo should contain about 200 cells, known as a blastocyst. At this point, there should be cellular differentiation, where there is a clear inner cell mass (which becomes the fetus) and an outer part, trophectoderm (which becomes the placenta). It can take 5-7 days for an embryo to become a blastocyst.
4 – Embryo biopsy
Biopsies are most safely taken from embryos that have successfully reached the blastocyst stage. In order to do this, the embryologist will take a biopsy of about 5 cells from the outer part of the trophectoderm (the part of the embryo that becomes the placenta). The biopsy is sent to the genetics company for analysis.
5 – Embryo cryopreservation
The blastocyst stage embryo, which is about 200 cells, is frozen after it is biopsied. The embryo will stay frozen at the fertility clinic (while the biopsy is sent away for testing). The process of freezing the embryo is called vitrification, which avoids the formation of ice crystals. Embryos can be frozen indefinitely, although storage policies differ by clinic.
