Fertilisation and Embryo Development
Once the eggs have been retrieved, they are carefully identified, washed and labelled. They are placed in a petri-dish with culture media and placed in an incubator for 3 to 4 hours. During this time, a semen sample is collected from the male partner and delivered to the lab where it undergoes processing referred to as "washing", which isolates the healthiest sperm. Once the sperm is washed, it is added to the eggs in correct concentrations to begin the process of fertilization. Alternately, for patients with problems such as male factor we may elect to use intracytoplasmic sperm injection (ICSI) to assist the fertilization process. After 18 hours, the eggs are examined for markers of successful fertilization. If normal fertilization occurs, then two to three of the resulting embryos will be selected and placed to the woman's uterus. Embryos are normally transferred between two to five days after the egg pickup. Note that not all eggs fertilize and not all fertilized eggs or 'zygotes' grow into good quality embryos. The embryos, which show slower development or get arrested, are discarded.