In Vitro Fertilization
IN VITRO FERTILIZATION (IVF) is a procedure wherein eggs are extracted from the patient and put in contact with the sperm of the partner or donor sperm in a lab for their fertilization.
There are many reasons why 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% achieve 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 reached the correct size, an injection of 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 from the ovaries. The egg retrieval is performed through the vagina and the patient is sedated so that she feels no pain.
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: the capacitated sperm is put in contact with the eggs. 18-22 hours later fertilization is checked.
b. ICSI: this is a micromanipulation technique in which the spermatozoon is injected into the egg. ICSI is used when there is a low sperm count, poor morphology or low motility. ICSI is also used when the sperm has difficulty penetrating the egg.
4. Embryo Transfer: 2 to 5 days after egg retrieval 1, 2 or 3 embryos are transferred to the patient´s uterus. The goal is to achieve a singleton pregnancy but depending on the age of the patient and the embryo quality, the patient and the doctor will decide on how many embryos to replace.
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 already been administered, egg retrieval is performed and there is no replacement of fresh embryos. Instead, the embryos are frozen and transferred at a later date. At other times (5%), hyperstimulation develops after embryo transfer.
The risk of multiple pregnancy increases with the number of embryos that are replaced. At present, there is a tendency to replace fewer embryos thus achieving a lower number of multiple pregnancies (10% of these cases).
Ectopic pregnancy is an embryo that implants outside the uterus. Ectopic pregnancies are slightly higher in women who have undergone assisted reproduction techniques than those women who conceive spontaneously. It can occur in 5% of cases.
There is a small risk of hemorrhage, infections, ovarian torsion and complications from anesthesia (<3%).
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