Fertilization of eggs in vitro occurs through either conventional in vitro fertilization (“Dish” insemination) or through intracytoplasmic sperm injection (ICSI). Conventional in vitro fertilization (Dish) involves placement of tens of thousands of moving sperm with eggs in a culture dish and incubating them overnight. ICSI is an alternate means of fertilization in which the sperm is injected into the egg. It is performed with the aid of a microscope and specialized microtools. By using ICSI, we can achieve fertilization rates similar to those seen with Dish insemination (typically above 70%), even in men with lower sperm quality.
Which method of fertilization your physician recommends will depend on the semen parameters of the male partner as seen through a semen analysis or previous attempts at intrauterine insemination (IUI). The three primary factors in determining the method of fertilization are: the concentration of sperm in the ejaculate (i.e. the sperm count), the motility (movement) of the sperm, and the morphology (overall shape and appearance). When established cutoffs for all three parameters are met, ”Dish” insemination is typically recommended and if any of these parameters are low, ICSI is typically recommended.
Regardless of semen parameters, ICSI is used on all frozen-thawed eggs, with all cryopreserved sperm, and in all cases where sperm are collected from the testes or epididymis.