In Vitro Fertilization
In vitro fertilization (IVF) is the joining of a woman’s egg and a man’s sperm in a laboratory dish. In vitro means “outside the body.” Fertilization means the sperm has attached to and entered the egg.
There are five basic steps to IVF:
Step 1: Stimulation, also called super ovulation.
Medicines, commonly called fertility drugs, are given to the woman to boost her egg production. Normally, a woman produces one egg per month. Fertility drugs tell the ovaries to produce several eggs. During this step, the woman will have regular transvaginal ultrasounds to examine the ovaries and blood tests to check hormone levels.
Step 2: Egg retrieval.
A minor surgery, called follicular aspiration, is done to remove the eggs from the woman’s body. The surgery is normally done as an outpatient procedure in the doctor’s office. The woman will be given medicines so she does not feel pain during the procedure. Using ultrasound images as a guide, the health care provider inserts a thin needle through the vagina and into the ovary and sacs (follicles) containing the eggs. The needle is connected to a suction device, which pulls the eggs and fluid out of each follicle, one at a time. The procedure is repeated for the other ovary. The woman may have some cramping after the surgery, but it usually goes away within a day. In rare cases, a pelvic laparoscopy may be needed to remove the eggs.
If a woman does not or cannot produce any eggs, donated eggs may be used.
Step 3: Insemination and Fertilization.
The man’s sperm is placed together with the best quality eggs and stored in an environmentally controlled chamber. The mixing of the sperm and egg is called insemination. The sperm usually enters (fertilizes) an egg a few hours after insemination. If the doctor thinks the chance of fertilization is low, the laboratory staff may directly inject the sperm into the egg. This is called intracytoplasmic sperm injection (ICSI). Many fertility programs routinely do ICSI on some of the eggs even if everything is normal.
Step 4: Embryo culture
When the fertilized egg divides, it becomes an embryo. Laboratory staff will regularly check the embryo to make sure it is growing properly. Within about 5 days, the embryo has several cells that are actively dividing.
Couple who have a high risk of passing a genetic (hereditary) disorder to a child may consider pre-implantation genetic diagnosis (PGD). The procedure is done about 3 -4 days after fertilization. Laboratory scientists remove a single cell from each embryo and screen the material for specific genetic disorders. According to the American Society for Reproductive Medicine, PGD can help parents decide which embryos to implant, which decreases the chance of passing a disorder onto a child. The technique is controversial and not offered at all centers.
Step 5: Embryo transfer
Embryos are placed into the woman’s womb 3 - 5 days after egg retrieval. The procedure is performed in the doctor’s office while the woman is awake. The doctor inserts a thin tube (catheter) containing the embryos into the woman’s vagina, through the cervix, and up into the womb. If an embryo sticks to (implants) in the lining of the womb and grows, pregnancy results.
More than one embryo may be placed into the womb at the same time, which can lead to twins, triplets, or more. The exact number of embryos transferred is a complex issue that depends on many factors, especially the woman’s age. Unused embryos may be frozen and implanted or donated at a later date.
Risks
IVF requires a significant physical, emotional, financial, and time commitment. Stress and depression are common among couples dealing with infertility. A woman taking fertility medicines may have bloating, abdominal pain, mood swings, headaches, and other side effects. Many IVF medicines must be given by injection, often several times a day. (The health care team will teach the couple how to properly mix the medicines and give a shot.) Repeated injections can cause bruising.
In rare cases, fertility drugs may cause ovarian hyperstimulation syndrome (OHSS). This condition causes a build up of fluid in the abdomen and chest. Symptoms include abdominal pain, bloating, rapid weight gain (10 pounds within 3-5 days), decreased urination despite drinking plenty of fluids, nausea, vomiting, and shortness of breath. Mild cases can be treated with bed rest. More severe cases require draining of the fluid with a needle.
Medical studies to date have concluded that fertility drugs in general are not linked to ovarian cancer.
Risks of egg retrieval include reactions to anesthesia, bleeding, infection, and damage to structures surrounding the ovaries, including the bowel and bladder.
There is a risk of multiple pregnancies when more than one embryo is placed into the womb. Carrying more than one baby at a time increases the risk of premature birth and low birth weight. (However, even a single baby born after IVF is at higher risk for prematurity and low birth weight.) It is unclear whether IVF increases the risk of birth defects.
Credit: National Institute of Health.