IVF Lab Procedures

Fertilization and Embryo Growth

As the eggs are retrieved, they are identified by the embryologist and placed into the incubator to avoid exposure to light, temperature and pH changes. Brief notes are made on the condition of the eggs. Normally two-thirds to three-fourths of the eggs will be mature and ready to be inseminated or injected by ICSI. Immature or post-mature eggs that may be retrieved have a much lower fertilization rate. After retrieval, the eggs are left in the incubator to complete their very final stage of maturation. This normally occurs between four and eight hours after the retrieval. Prior to retrieval, a sperm sample is collected from the male partner and processed by density gradient washing techniques. This process allows us to collect the most viable sperm to be used for insemination or ICSI. The day after retrieval, called Day 1, begins with the assessment of fertilization and the separation of those normally fertilized eggs. Cell division or cleaving will occur after the intermingling of the chromosomes overnight. We typically see the second cleavage division from a two cell to a four cell embryo on Day 2. Embryos will be assessed on Days 2 and 3 for transfer or placement into blastocyst media until day 5 or 6.

Embryo Assessment

High quality embryos have a homogenous or light non-grainy cytoplasm within the cells. The membranes should be very smooth and not rough or jagged. The cells should be approximately the same size, touch each other, and form a round ball within the zona pellucida or shell. The zona pellucida itself should be clear and not too thick. A common finding in embryos is fragmentation; individual cells within the embryo may have broken up and appear as fragments inside the zona. Generally, less fragmentation is better. Prior to transfer, the embryologist will have evaluated the embryos for their morphological appearance and graded them on a scale of 1 to 4. This assessment gives us a subjective estimate of the likelihood of implantation once the embryos are replaced into the uterus. Those that have the best characteristics and are cleaving normally are believed to have a higher chance of implantation; these will be chosen for transfer.

This assessment is subjective and embryos that have poor morphological characteristics still have the ability to implant, although, in our experience, at a rate less than those with better characteristics. The number of embryos transferred depends on the quality of the embryos, the age of the woman, and the day of transfer (Day 3 vs. Day 5, 6).

Identification and Handling of Sperm, Eggs, and Embryos

We make every effort to assure couples that the eggs, sperm, and embryos in our possession in the laboratory are always handled with trust, respect, expertise, and care. Our labeling process and a series of checks and balances are designed to ensure matching you to your eggs, sperm, and embryos. This is a constant priority throughout the IVF process. A review of the precautions and safe guards are outlined below for your information.
 

Fertilized Egg	2 Cell Embryo	8 Cell Embryo	Blastocyst