During natural conception, an egg and sperm fertilize inside a woman’s body, in the fallopian tube. The fertilized egg then travels to the uterus, where it attaches to the lining and grows into a baby. However, sometimes the process of natural conception encounters a glitch in the system and assisted reproductive technology called in vitro fertilization (IVF) is needed to overcome it.
There are five basic steps involved in IVF, they are stimulation, egg retrieval, in vitro fertilization, embryo culture and embryo transfer. After these five steps, monitoring and support of the pregnancy must be maintained.
During a natural cycle, a woman’s body produces only one egg. To increase the chances of success, fertility medications are used to encourage the ovaries to produce multiple follicles, which contain a single egg each, at the same time. Regular transvaginal ultrasounds are used to monitor the growth of the follicles until they are mature. Blood tests also verify hormone levels have reached adequate levels indicating maturity.
This is a minor surgical procedure often done under conscious sedation, general anesthesia or regional anesthesia. Once under anesthesia, an ultrasound guided needle is inserted through the vaginal wall into the ovary where the follicles are located. The follicles are individually aspirated of their egg and fluid using a suction device. This is repeated for each ovary. After the procedure, the woman may experience some cramping and constipation.
In Vitro Fertilization
After retrieval, the eggs are taken to the fertility laboratory for evaluation of quality and maturity. Eggs meeting the standard set by the lab to continue with the process are then fertilized either by mixing the sperm and egg together allowing them to fertilize naturally or through intracytoplasmic sperm injection (ICSI). ICSI is used when the chances of natural fertilization are low. The lab staff selects one sperm to inject into each egg. For some clinics, ICSI is used routinely even if everything appears normal.
Once an egg has been fertilized with a sperm it is placed in a culture medium and it begins cellular division. After it has begun this phase it is called an embryo. The embryo will be cultured in the lab for approximately 3-5 days. During this time, preimplantation genetic diagnosis (PGD) can be used to screen the embryo for genetic disorders allowing only genetically normal embryos to be transferred back into the woman’s uterus.
Transferring the embryos back into the womb is done while the woman is awake. The doctor inserts a thin catheter containing the embryos through the cervix and into the uterus. Often this will be guided by ultrasound, and the embryos will look like a tiny shooting star on the monitor as they leave the catheter. Elective single embryo transfer to minimize multiples has become the new recommendation as success rates for this process have dramatically improved. Your doctor will recommend the best number of embryos to transfer to maximize your chance of success. Embryos that are not transferred can be cryopreserved for a later frozen embryo cycle.
Approximately two weeks after embryo transfer there will be a blood test to determine the presence of the pregnancy hormone in the blood.
Consideration should be given ahead of time as to what will be done with any unused embryos. Often after a successful pregnancy the leftover embryos seemingly become forgotten and indefinitely remain in storage, even after the parents have completed their family. Several dispositions are available including donation to another infertile couple, donation to research or compassionately transferred during a non-fertile time of the woman’s cycle.