Ultrasound picture of Ovary: Injections of Lupron, Metrodin, Pergonal or Humegon allow the ovaries to develop many follicles as seen in this ultrasound immediately prior to egg retrieval.
Fertilized oocyte (2PN embryo): Immediately after fertilization, the egg contains two pronuclei. Each contains the chromosomal material from one of the genetic parents.
Four cell embryo: Each of the cells is called a blastomere. The embryo is surrounded by a protein matrix "shell" called the zona pellucida.
Eight cell embryo: On the third day after the egg retrieval eight cell embryos can be transfered to the uterus. On average, 10-15% of embryos such as this will implant after being transfered.
Hatched Embryo: Prior to implantation, the embryo, now at the blastocyst stage, must hatch out of the zona pellucida. Only then can it attach to the mother's endometrial lining.
