IVF treatment begins on the third day of menstration when ovarian stimulation will begin with medications to stimulate development of follicles in the ovaries. . The patient undergoes close monitoringand ten days of injections. Once the specialist handling the case determines that the eggs are mature enough, another medication, human chorionic gonadotropin will be givento the patient. The doctors then wait 42 hours to retrieve eggs from the ovaries by piercing the vaginal wall with a needle. Follicles and fluid will go immediately to the IVF lab for the identification of the eggs. Typically, from ten to thirty eggs will be retrieved. This retrieval process takes about 20 minutes. The patient will be under conscious sedation or general anesthesia.
Fertilization is the next step, beginning with the stripping of surrounding cells from the eggs. Meanwhile, semen is being prepared by the removal of inactive cells and seminal fluid. Semen may also be collected ahead of time and frozen. Sperm and egg(s) are incubated together for about 18 hours. The egg is expected to be fertilized by that time and will show two nuclei—one female, the other male—that will fuse to become a single nucleus. The appearance of the two pronuclei indicates that a successful fertilization has occurred. Next, the fertilized egg is placed in a special growth medium, where it will stay for about 48 hours at which time the egg will have six to eight cells.
In some cases, gamete intrafallopian transfer will take place instead, where eggs are removed and placed in one of the mother’s fallopian tubes with the sperm. The fertilization will take place within the mother’s body and is more accurately called in vivo fertilization.
Embryos are transferred after three days. However, they are sometimes kept in a specially-prepared culture for about 5 days. Time spent in this culture seems to improve pregnancy rates. The doctor makes decisions regarding which and how many embryos will be transferred and then implants them in the mother’s uterus using a thin plastic catheter.
The doctor’s decision about how many embryos to implant is based on several things, beginning with the number available. Factors such as age of mother and other health and diagnostic factors will be taken into account. Many countries limit the number to be transferred in a younger mother to three. It’s generally felt that multiple pregnancies are more risky than single births. However, if the treating doctor feels that the chances for implantation are not great in this particular case, he or she may choose to implant more rather.