Using Lupron along with a stimulation cycle completely turns off the pituitary and prevents a premature LH surge that would interfere with the proper development of the large number of eggs necessary for IVF. Early Development of the Fertilized Egg Over the next three days the fertilized egg first divides cleaves into two, then four, then eight cells. As you can see, when it comes to getting pregnant, sperm health cannot be neglected… Given the difficulty of the journey and the possible hazards along the way, one basic axiom is certainly true: Motility may matter as much as sperm count when it comes to getting pregnant. Each month, from the time of sexual maturity on, about one thousand undeveloped eggs, or oocytes, leave their prolonged resting phase and start to mature. This process is called down regulation.
Before egg and sperm can ever meet up in the fallopian tube, the egg must be matured and extruded from the ovary in a process called ovulation.
Sperm Health: How Long Sperm Live & Details of the Journey