In Vitro Fertilization (IVF) is characterized by the union of an egg and a sperm (fertilization) is performed in the laboratory, i.e. outside of the womb. This technique requires ovarian stimulation using gonadotropins subcutaneously and ultrasound monitoring. Analytical control of the estradiol hormone is always required to assess egg maturity. Ideally 8-10 mature eggs will be retrieved for a good chance of success.
After a period of about twelve days of treatment, the mature eggs are retrieved and taken into the laboratory. The egg collection will be performed in an operating theatre; the patient will be sedated, and it is performed inserting an ultrasound probe and a fine needle to collect the eggs from the follicles. This process usually takes 10-15 minutes. After which, the patient is discharged and a rest of 24-48 hours is recommended.
Once in the laboratory, the obtained eggs can be inseminated with partner’s sperm or donor sperm, either conventionally, i.e. putting each egg in a dish along with several thousand sperm and waiting 24 hours until fertilization occurs, or fertilizing each egg using ICSI, a technique that involves injecting an individual sperm through a micropipette into each egg under a special microscope. Currently, some centers have a new microscope that allows this technique to be performed with much higher magnification, being much more precise in the selection and injection of sperm, it is called IMSI.
Once the egg and sperm are fertilized, it is now called an embryo which is left to grow in special culture media, usually for three days following a rigorous process of observation of their morphology and cell number. Not all embryos develop normally, some stop growing (cell block) and must be discarded.
In some cases the embryo is left to grow up to six days (blastocyst stage) in order to select more rigorously their morphology and decide which are most likely to implant in the uterus of the patient after Embryo Transfer and which are susceptible for freezing (Embryo Vitrification). Whether on day 3 or day 6, the embryo transfer is performed in the same way. One or two embryos are deposited into the uterus through a special tube (catheter). It is a simple and painless procedure, which is performed on an outpatient basis and afterwards the patient is recommended to rest for 24-48 hours.
On the day of transfer, remaining viable embryos are frozen using a vitrification process, for future transfer in a subsequent cycle without the need of ovarian stimulation and egg collection.