In Vitro Fertilization (IVF)
The in vitro fertilization (IVF) procedure is used to treat a variety of conditions that impair fertility, including tubal disease, endometriosis and male factor problems. First, fertility drugs stimulate the ripening of several eggs, which are then removed using ultrasound guidance and IV sedation.
Outside the woman's body (in vitro), sperm are added to the eggs and incubated. The resulting embryos are then transferred into the woman's uterus, usually three to five days after the initial procedure. The hope is that one or more of the embryos will implant onto the uterine wall, beginning a pregnancy.
The steps in the IVF process are explained below.
The first step requires that the woman take fertility medications to stimulate the development and growth of multiple follicles in her ovaries. The follicles contain the woman’s oocytes. During this time the patient is monitored with blood tests and vaginal ultrasound exams to monitor the development of her follicles. When the follicles reach a mature size, the patient is scheduled for her oocyte retrieval.
The oocyte retrieval is an outpatient procedure done in the operating room at Community Hospital North, and is performed by a transvaginal ultrasound guided method. The patient receives anesthesia, and the physician does a transvaginal ultrasound exam to visualize the follicles in the ovaries. A thin needle is then passed through the vaginal wall and, under ultrasound guidance, the needle is inserted into each follicle and the follicular fluid aspirated into a test tube. The follicular fluid is then examined by the embryologists in the lab to identify the oocytes. When all the follicles have been aspirated, the patient goes to the recovery area and goes home-usually about 1-2 hours after the procedure.
A sperm sample is obtained from the male partner, and a complete semen analysis is performed on the sample. The sample is washed to separate the most highly motile sperm from the sample, and several thousand highly motile sperm are added to the eggs to achieve fertilization.
Intracytoplasmic sperm injection (ICSI)
ICSI is a technique in which a single sperm cell is injected directly into the egg to achieve fertilization. With ICSI, men with very poor semen analyses can achieve fertilization and become biologic parents. ICSI can even be used in men with no sperm in the ejaculate. For such men, sperm can be obtained directly from the epididymus (site where sperm is stored prior to ejaculation) or can be obtained directly from the testicle either by a fine needle aspiration or from a testicular biopsy.
The day following insemination, eggs can be assessed to determine if fertilization has occurred. The following day, the fertilized eggs should develop into embryos, and should reach about a 2-4 cell stage of development. By day three following retrieval the embryos generally should reach around a 6-10 cell stage of development.
Preimplantation diagnosis (PGD)
Preimplantation diagnosis (PGD) is a technique that can be used to diagnose genetic conditions in an embryo prior to embryo transfer. This way, embryos that carry certain genetic disorders can be detected and the patient can opt to not have affected embryos replaced at the time of embryo transfer. PGD can be used to diagnose lethal genetic disorders (depending on the affected gene) and can be used to assess whether there are a normal number of chromosomes in the embryo. Assessment of chromosome numbers by PGD can be useful in women who have experienced multiple miscarriages.
Advances in the understanding of the growth requirements for embryos has led to better laboratory conditions to support growth of embryos in vitro. One such advancement is blastocyst transfer, also known as day five embryo transfer. The blastocyst stage is the stage at which the embryo normally exists within the uterine cavity, and is the stage at which embryos normally implant inside the uterus. By culturing embryos to blastocyst before embryo transfer, fewer embryos can be transferred, thus limiting the possibility of high order multiple pregnancies (triplets or greater) that put both the mother and babies at risk. Though fewer embryos are transferred, pregnancy rates are similar to, if not higher than, when embryos are transferred earlier in the cycle (day three). By waiting until day five, the embryos indicate by their rate of development which ones have the highest potential to implant.
Embryo transfers are generally done on day three or day five after retrieval. To transfer the embryo, the physician passes a thin catheter containing all the embryos though the cervix into the uterus and the embryos are gently deposited in the uterine cavity. Embryo transfers are generally done during an abdominal ultrasound so the physician can visualize the catheter inside the uterus during the transfer procedure.
Embryo cryopreservation (freezing)
In many IVF cycles there are more eggs produced and embryos created than are safe to transfer back to the uterus. Embryo cryopreservation is a procedure in which the laboratory freezes embryos that are not transferred, such that they can be used in a subsequent attempt to achieve pregnancy. Embryos can be frozen successfully at any stage of development, from 1-6 days after the egg retrieval procedure. There are two advantages to embryo freezing:
- All the eggs obtained from a single retrieval cycle are inseminated, thus increasing the ability to select the best quality embryos for transfer.
- For a subsequent attempt at pregnancy the patient does not have to undergo another complete IVF cycle with ovarian stimulation and egg retrieval.