Vaginal ultrasound guided aspiration is used to harvest the egg(s). Intravenous pain medication is often used to make the woman comfortable. Timing is crucial. If the egg harvest is done too early, the eggs won't fertilize; if it is done too late the eggs may have been released spontaneously or may be too mature.
The husband will be asked to provide a fresh semen specimen. After a process called sperm washing, anywhere from 50,000 to one million sperm are mixed with the eggs and allowed to incubate for 14-18 hours. The fertilized eggs (embryos) are then transferred to a new growth medium. The embryologist will look for embryos that have two pronuclei, indicating normal fertilization has occurred. 38-40 hours later, the embryos are examined and assessed to determine how many blastomeres (cells in the developing embryo) are present and how even the blastomere's walls