In Vitro Fertilization
In In vitro Fertilization (IVF), eggs are extracted from the patient and in the lab the eggs are put in contact with the sperm of the partner or donor sperm to create embryos.
This procedure was first used in England in 1974. There are many reasons that IVF is carried out: obstructed fallopian tubes, hormone imbalance, endometriosis, a low sperm count or low quality sperm or failure to achieve pregnancy through artificial insemination.
Pregnancy rates in IVF vary according to the age of the woman, the diagnosed diseases and the semen. Around 35-40% achieves pregnancy. In women under 35, pregnancy rates are as high as 44%.
IVF can be divided into 4 phases:
1. Ovarian stimulation: meds are administered to stimulate the ovaries increasing the number of follicles that mature during the cycle. In each follicle there is one egg. Once the follicles have achieved the correct size, hCG is administered and 36 hours later egg retrieval is performed.
2. Egg retrieval: the goal of the retrieval is to extract the mature eggs. We sedate the patient so that she feels no pain. The egg retrieval is performed through the vagina and it is ultrasound-guided.
3. Fertilization in the laboratory: eggs can be fertilized in 2 different ways: by conventional IVF or by ICSI (Intracytoplasmatic Sperm Injection):
a. Conventional IVF: a drop of capacitated sperm is place on each egg: 18-22 hours later fertilization is checked.
b. ICSI is a micromanipulation technique. The egg is secured and a spermatozoon is injected into the egg. ICS is used when there is a low sperm count, poor morphology of low motility. Other times ICSI is used when the sperm does not penetrate easily into the egg.
4. Embryo Transfer: 2 to 5 days after egg retrieval and once fecundation has been achieved 1,2 or 3 embryos are replaced. The goal is to achieve a singleton pregnancy but depending on the age of the patient and the embryo quality, the patients and the doctor will decide on how many embryos to replace.
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Riesgos
Ovarian hyperstimulation syndrome is an exaggerated response to the stimulation treatment. It can be classified in 3 degrees: mild, moderate and severe. It can be prevented by correct dosage of stimulation medication, but some patients are hypersensitive to these meds and even with a very low dosage develop an elevated number of follicles. In this case, to prevent hyperstimulation the cycle is cancelled and hCG is not administered. If hCG has been administered, egg retrieval is performed and embryos are frozen and there is no replacement of fresh embryos. At other times, hyperstimulation develops after embryo transfer.
The risk of multiple pregnancy increases with the number of embryos that are replaced. At present, there is a clear tendency to replace fewer embryos thus achieving a lower number of multiple pregnancies.
Ectopic pregnancy is an embryo that implants outside the uterus. Ectopic pregnancies are slightly higher in women who undergo assisted reproduction techniques than those women who conceive spontaneously.
There is a small risk of hemorrhage, infections, ovarian torsion and complications from anesthesia.
