Embryos are generally transferred to the woman’s uterus at the 2-8
cell stage. Embryos may be transferred anytime between day 1 through day
6 after the retrieval of the egg, although it is usually between days
2-4. Some clinics are now allowing the embryo to reach blastocysts stage
before transferring, which occurs around day 5.
7.4 million women, or 11.9% of women, have ever received any infertility services in their lifetime.
(Source CDC National Survey of Family Growth, 2006-2010)
When Embryo Transfer is Needed
IVF and embryo transfer is needed in cases where natural fertilization is not an option or has difficulty occurring. There are many reasons for embryo transfer, including:
- Ovulation disorders: If ovulation is infrequent, fewer eggs are available for successful fertilization.
- Damage to Fallopian tubes: The Fallopian tubes are the passageway through which the embryos travel to reach the uterus. If the tubes become damaged or scarred, it is difficult for fertilized eggs to safely reach the womb.
- Endometriosis: When tissue from the uterus implants and grows outside of the uterus. This can affect how the female reproductive system works.
- Premature ovarian failure: If the ovaries fail, they do not produce normal amounts of estrogen or release eggs regularly.
- Uterine fibroids: Fibroids are small, benign tumors on the walls of the uterus. They can interfere with an egg's ability to plant itself in the uterus, preventing pregnancy.
- Genetic disorders: Some genetic disorders are known to prevent pregnancy from occurring.
- Impaired
sperm production: In men, low sperm production, poor movement of the
sperm, damage to the testes, or semen abnormalities are all reasons
natural fertilization may fail.
Types of embryo transfer
In order to extract and fertilize the eggs during IVF, fertility doctors generally follow the same process every time. Once fertilization has occurred, there are a few different options available for embryo transfer:
Fresh embryo transfer: Once eggs have been fertilized, they are cultured for 1-2 days. The best embryos are chosen to transfer directly to the woman's uterus.
Frozen embryo transfer: Any healthy embryos that were not used in the first transfer can be frozen and stored for future use. These can be thawed and transferred to the uterus.
Blastocyst embryo transfer: If many healthy embryos develop after the fertilization, it is common to wait to see if the embryos develop into blastocysts.
Assisted hatching (AH): AH is a laboratory procedure that is sometimes done along with in vitro fertilization (IVF) treatment. IVF involves mixing eggs with sperm in a laboratory (as opposed to within a woman's body like in natural conception).
Embryo Transfer Procedure
Anesthesia is often not necessary, although a sedative may be used. An ultrasound may be used to help guide the physician as he transfers the embryos. A predetermined number of embryos are loaded into a fine transfer catheter that passes through the vagina and cervix, into the uterus.
The embryos are deposited from the catheter into the uterus. Following this procedure, the patient usually remains in a recovery room resting on her back and is discharged 4-6 hours after the procedure.
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