How IVF works

Introduction


IVF stands for in vitro fertilization, in other words “fertilization in the glass”. Another common moniker is “test tube baby”. To perform IVF female eggs are fertilized with the male partners sperm in the laboratory. The resulting embryos from this process are transferred into the female partner’s uterus (womb). Typically the created embryo(s) are grown and cultured in the lab for 3-5 days.

One of the great advantages of IVF is that it can treat many causes of infertility. These conditions include, tubal blockage, problems with ovulation, problems with the way the sperm and egg interact, poor sperm quality or quantity, older patients, problems with the cervix and many more.

Another great advantage of IVF is that it can be used to make specific diagnoses. Since the embryo is created in the lab it gives physicians the ability to test the embryos for any genetic or chromosomal problems. IVF therefore can be used to diagnose inheritable diseases. Some of the most common diseases tested are cystic fibrosis, sickle cell disease, and chromosomal problems such as Downs’s syndrome and Turner’s syndrome. Click For More On PGD and CGH

Finally IVF has the highest success rate in achieving a pregnancy for couples. It also affords couples the option to store and freeze extra embryos that are created for future fertility.


Egg Production: (ovarian hyperstimulation)


One of the goals during IVF is to allow the ovaries to produce multiple eggs. To stimulate the ovary to do this, the patient is given hormonal medication (FSH analogues). FSH (follicle stimulating hormone) is the hormone that is naturally responsible for stimulating the ovary. The patient is given a daily or twice daily dose of FSH. This allows the ovary to produce more than the usual 1 egg. The patient is then monitored regularly to evaluate how she is responding to the medication.

Monitoring is done in two ways; first the patient is monitored with Ultrasound evaluations. These ultrasounds allow the doctor to visualize how many eggs are being produced. Eggs develop and mature in cysts (also called follicles), by measuring these cysts (follicles) the physician can determine when the eggs are mature. Second the patient is monitored by measuring estradiol levels (estrogen). The estradiol levels also help the physician understand how well a patient is stimulating.

The typical patient is given FSH and stimulated for about 10-12 days. Once it is determined that the eggs are mature the physician will simulate ovulation of the eggs by giving a medication called hCG (human chorionic gonadotropin). The hormone mimics the hormone that naturally causes women to ovulate.

An egg retrieval procedure is then scheduled.

Egg Retrieval


This procedure is performed usually 30-40 hours after hCG, or ovulation induction is administered. The egg retrieval must be done prior to the patient ovulating on her own. The eggs are retrieved using a needle that is guided by ultrasound. The patient is given light anesthesia.

Egg Fertilization


Once the eggs are retrieved they are identified under the microscope. Each egg is typically surrounded by cells. The embryologist will “strip” the cells away from the egg. Sperm is also prepared for fertilization by “washing” the sperm. This process removes non-motile sperm and seminal fluid. Once the preparation process is complete the sperm and egg are brought together. There are two methods in which this can be performed. The first method is an incubation method; where approximately 75,000 sperm are incubated with each egg in culture media. 18 hours later the embryologist evaluates the eggs to visualize if fertilization occurred. The second method utilized is ICSI (intracytoplasmic sperm injection), Where a single sperm is selected and injected directly into the egg.

     Egg after stripping                   ICSI                        Fertilization occured              IVF Microscope

 

Embryo Culture


Eggs that fertilized successfully are transferred into culture media to promote the growth of the now newly formed embryo. Embryos are typically kept in this growth media for 48-72 hours at which time they should grow to be 6-8 cell embryos. Embryos at this stage can be transferred back into the patients uterus (womb). Alternately these embryos can be placed into a different culture media and grown to what is called the blastocyst stage (5 day old embryos). Embryos can be transferred on day 5 as an alternative method. Patients should discuss thoroughly the benefits and disadvantages of day 3 or day 5 transfers.

             4 Cell Embryo                       8 Cell Embryo                              Blastocyst

 

Embryo Transfer


The embryo transfer procedure is the procedure that places the embryo(s) in to the patient’s uterus (womb). Embryo transfer is done by placing the best embryo(s) into a thin plastic catheter; this catheter is then passed through the vagina and cervix into the uterine cavity (womb). Once in the appropriate location inside the uterus the embryos are injected inside. Very often physicians will utilize an ultrasound to visualize the tip of the catheter and ensure its proper placement.

The embryos chosen for transfer are evaluated by the embryologist and physician to determine the best quality embryos. The number of embryos transferred depends on the patient’s age, history, embryo quality, risk assessment, risk tolerance, and other diagnostic and clinical indicators.