A quick health class refresher: During ovulation women typically release one egg from their ovaries into one of the fallopian tubes. With IVF, follicle-stimulating hormones (FSH) are injected into the ovaries so they produce multiple eggs. Before the eggs are released during ovulation, they are retrieved with a needle, with the aim of gathering as many as possible, usually between eight and 15. "We work with the existing number of eggs and rescue eggs that may have been destined to die that month,” explains Dr. Sonya Kashyap, medical director at Vancouver's Genesis Fertility Centre . Then, as the name suggests, egg and sperm are combined in vitro — outside of the body, in a lab — to make an embryo. Embryos can be either frozen for future pregnancy attempts or transferred back into the patient's uterus within three to five days. At this point, they will have multiplied and contains several dozen or even a hundreds of cells and have a higher chance of implanting to the uterine wall.