There are two ways to fertilize eggs in the laboratory.
When good fertilization is expected conventional insemination is used. With conventional insemination the sperm and egg are placed together in a nutrient solution inside of a petri dish. Typically around 50,000-100,000 sperm are placed around each egg. The dish is housed in an incubator overnight to keep the egg and sperm at room temperature. They are left alone for 16 to 20 hours at which point the embryologist can check the eggs to see if the sperm was able to fertilize the egg normally.
ICSI (intracytoplasmic sperm injection)
When there is a higher likelihood that normal fertilization may not occur we opt to use a technique called ICSI (intracytoplasmic sperm injection). We may have a suspicion the fertilization could be more challenging in situations where the number of sperm are low, the percentage of moving sperm is low or there is a high number of abnormally shaped sperm. When sperm is extracted directly from the testicle by a procedure called testicular sperm extraction (TESE) ICSI is always used. ICSI is also occasionally used in situations where there are a very low number of eggs to fertilize. ICSI is always utilized to fertilize eggs that have been frozen previously for fertility preservation.
With ICSI the embryologist removes the cells that normally surround the egg and washes the sperm in a special solution, all with the assistance of a high-powered microscope. Once the embryologist is able to visualize the sperm, they then choose a good looking sperm that is moving well and suck that sperm into a very fine pipette with a sharp tip. This delicate procedure requires the embryologist to gently hold a single egg steady with one pipette, and then inject the loaded sperm directly into that egg. This procedure is repeated over and over until all the eggs have been injected with sperm.
The process afterward is the same as with conventional insemination in that the eggs (each with an injected sperm inside of it) are kept in an incubator overnight and checked in the following morning to see if normal fertilization occurred.
There are some studies that suggest that ICSI embryos may have a higher rate of aneuploidy (abnormal chromosome count) however this higher rate is thought to likely occur because men with severe male factor have more chromosomal abnormalities in their sperm.
ICSI provides a safe and effective way to fertilize eggs that may otherwise have no ability to be fertilized. Very little if any harm is incurred by the egg in the hands of our expert embryology team.