IN VITRO FERTILIZATION AND EMBRYO CULTURE
After eggs are retrieved, they are transferred to the embryology laboratory where they are kept in conditions that support their needs and growth. The eggs are placed in small dishes containing “embryo culture medium” which is special fluid made to resemble that found in the fallopian tubes to support development of the embryos. The dishes containing the eggs are then placed into incubators, which control temperature, humidity, gas, and light at just the right levels.
A few hours after egg retrieval, sperm are placed in the culture medium with the eggs, or individual sperm are injected into each mature egg in a technique called Intracytoplasmic Sperm Injection (ICSI). The eggs are then returned to the incubator, where they remain to develop. The dishes are inspected periodically so the development of the embryos can be assessed.
The day after the eggs have been inseminated, they are examined for signs that the process of fertilization is underway. At this stage, normal development is evident by the fertilized egg having 2 nuclei; this is called a zygote. Two days after insemination, normally developing embryos would have divided into between 2 to 4 cells. Three days after insemination, normally developing embryos would have divided into between 4 to 8 cells. Up to 5 to 7 days after insemination, normal embryos would have developed to the blastocyst stage, which is typified by an embryo that has 200 or more cells, an inner fluid-filled cavity and a small cluster of cells called the inner cell mass.
It is important to note that since many eggs and embryos are abnormal, it is expected that not all eggs will fertilize and not all embryos will divide at a normal rate. Some embryos may stop growing. Even if your embryo(s) develop normally in the lab you still may not get pregnant.
This means that not all embryos developing at the normal rate are also genetically normal, and not all poorly developing embryos are genetically abnormal. Nonetheless, their visual appearance is the most common and useful guide in the selection of the most appropriate embryo(s) for transfer.
In spite of reasonable precautions, any of the following may occur in the lab that would prevent the establishment of a pregnancy:
Fertilization of the egg(s) may fail to occur.
One or more eggs may fertilize abnormally resulting in an abnormal number of chromosomes in the embryo; these abnormal embryos cannot be transferred.
The fertilized eggs may fail to develop into embryos, or the embryos may not develop normally.
Rarely, the eggs or embryos may be harmed by contact with bacteria.
Laboratory accident or human error can occur which could lead to the loss of eggs, sperm and embryos.
Other unforeseen circumstances may prevent any step of the procedure to be performed or prevent the establishment of a pregnancy.
Hurricanes, tornadoes, floods, earthquakes, fires or other “acts of God” (including bombings or other terrorist acts) could destroy the laboratory or its contents, including any sperm, eggs, or embryos being stored there.
Quality control is the process of running tests to ensure lab conditions are the best they can be to help embryos grow. Sometimes immature or abnormal eggs or embryos that have not developed normally can be used for quality control checks before they are discarded. None of the material that would normally be discarded will be utilized to establish a pregnancy or a cell line unless you sign other consent forms to allow the clinic to use your eggs, sperm or embryos for research purposes.