Protecting your mental health during fertility treatment. At the same time, the female nucleus which is sitting on the opposite side of the egg is triggered to undergo its second meiotic division shortly after sperm penetration and become the female pronucleus. The cystlike structure that forms monthly from the ruptured follicle is called the corpus luteum. Over the next three days the fertilized egg first divides cleaves into two, then four, then eight cells. It is thought that the more relaxed and spontaneous your sex life, the more likely that you will conceive.