A frozen embryo transfer (FET) is a cycle where embryos which were frozen in the previous fresh IVF cycle are thawed and transferred into a woman’s uterus. This avoids the need to undergo another cycle of hormone stimulation and egg collection.
The procedure will be explained to the patient as it has multiple steps:
Medications for oocyte maturation: When the follicles are ready for egg retrieval, generally after eight to 14 days, human chorionic gonadotropin (HCG) or other medications are given to help the eggs mature.
Egg retrieval usually planned 34 to 36 hours after the final injection and before ovulation. This procedure is done under sedation to make it pain-free.
If a partner’s sperm is used, he’ll provide a semen sample through masturbation the morning of egg retrieval. Other methods, such as testicular aspiration — the use of a needle or surgical procedure to extract sperm directly from the testicle — are sometimes required or donor sperm also can be used.
Fertilization can be attempted using two common methods:
Intracytoplasmic sperm injection (ICSI): In ICSI, a single healthy sperm is injected directly into each mature egg. ICSI is often used when semen quality or number is a problem or if fertilization attempts during prior IVF cycles failed.
The process most commonly used for embryo freezing is called vitrification. In this process, the water inside the cell is replaced with substances known as cryoprotectant. It is followed by very rapid cooling that helps prevent ice crystals from forming inside the cells and thus increases the survival of embryos during the thawing process. Embryos are then placed in plastic straws and are labelled with the patient’s name and identification number. Embryos can be frozen for many years by this process in the tanks filled with liquid nitrogen.
Frozen Embryo transfer:
After the embryo transfer, the patient can resume normal daily activities.
Frozen embryo transfer is associated with very minimal risks as compared to fresh embryo transfer where the risk of OHSS is present.
About 12 days to two weeks after embryo transfer, blood test (beta-hCG) is used to detect whether the patient is pregnant.
If b-HCG negative i.e. not pregnant, a woman is advised to stop taking progesterone and is likely to get period within a week. If she has any remaining embryos frozen, then she will be offered frozen embryo transfer in next cycles.
There is a risk of losing embryos during the freezing and thawing process, which could reduce the success rates.
Multiple pregnancies: when more than one embryo is transferred, there is a risk of multiple pregnancies, which carry a risk of early labour and delivery of low birth weight babies.
Ectopic pregnancy: when the fertilized egg implants outside the uterus, usually in a fallopian tube. The fertilized egg can’t survive outside the uterus, and there’s no way to continue the pregnancy.
Birth defects: The age of the mother is the primary risk factor in the development of birth defects.
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