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.
Why it’s Done
Embryo freezing might be an option if the couple is not ready to become pregnant now but want to try later.
Sometimes during ovarian stimulation, hormones are produced in very high number due to the development of a large number of follicles. In this condition, embryos are frozen to avoid the development of a serious complication which is ovarian hyperstimulation syndrome (OHSS)..
If during the IVF cycle, a large number of embryos are created, usually one or two embryos are transferred and remaining embryos are frozen to avoid achieving multiple pregnancy and associated risks..
Genetic disorders: If either couple is having some genetic disease, which can be inherited by the offspring, they are offered pre-implantation genetic screening. Here some cells are biopsied from the embryo and genetic analysis is done. Healthy embryos which are devoid of any disease are then transferred.
Fertility preservation: If a woman is undergoing cancer treatment such as radiation or chemotherapy that could harm your fertility, freezing embryos is an option. These can be transferred later after cancer treatment.
How You Prepare
The first step is to approach a reproductive endocrinologist who is an expert in the field. Before starting an IVF cycle, both partners are likely to undergo various screening.
Ovarian reserve testing is done to determine the quality and quantity of eggs. It is checked by doing blood levels of Follicle-stimulating hormone (FSH), Estradiol and Anti Mullerian hormone in the initial days of the menstrual cycle. Also, ultrasonography is done to see the number of eggs in each ovary, to determine how the ovary will respond to fertility medication
Uterus lining will be examined before starting the IVF. It might include a hysteroscopy — in which a thin, flexible, lighted telescope (hysteroscope) is inserted through the vagina and cervix into the uterus.
For men: Semen analysis: done as part of your initial fertility evaluation
For a couple: Infectious disease screening includes HIV, Hepatitis B and C.
What you can expect
The procedure will be explained to the patient as it has multiple steps:
Hormonal medicines (injection FSH/HMG) are given to stimulate the ovaries to produce multiple eggs rather than the single egg that normally develops each month. Multiple eggs are needed because some eggs won’t fertilize or develop normally after fertilization.
Monitoring: Vaginal ultrasound of ovaries is used to monitor the development of follicles where eggs mature. Additionally, blood tests are done to measure the response to ovarian stimulation medications — estrogen levels typically increase as follicles develop, and progesterone levels remain low until after ovulation
Medications to prevent premature ovulation: prevent the body from releasing the developing eggs too soon.
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.
Transvaginal ultrasound aspiration is the usual retrieval method. Under ultrasound guidance, a thin needle is inserted into an ultrasound guide to go through the vagina and into the follicles to retrieve the eggs..
The eggs are removed from the follicles through a needle connected to a suction device. Multiple eggs can be removed in about 20 minutes. The chances of conceiving increase with the number of eggs that are retrieved.
After egg retrieval, the patient may experience cramping and feelings of fullness or pressure.
Mature eggs are placed in a nutritive liquid (culture medium) and incubated. Eggs that appear healthy and mature will be mixed with sperm to attempt to create embryos.
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:
Conventional insemination: In this, healthy sperms and mature eggs are mixed in a culture medium, where the sperm fertilizes the egg using its natural motility.
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.
Medications to prepare the lining of uterus: On the day of egg retrieval, progesterone supplements are given to make the lining of your uterus more receptive to implantation. Embryo transfer usually takes place two to five days after egg retrieval.
A number of embryos to be transferred: The number of embryos transferred is typically based on age and number of eggs retrieved. Since the rate of implantation is lower for older women, more embryos are usually transferred. Extra embryos can be frozen and stored for future use for several years
The procedure is usually painless, although the patient might experience mild cramping. A long, thin, flexible tube called a catheter is inserted in the vagina, through the cervix into the uterus. A syringe containing one or more embryos suspended in a small amount of fluid is attached to the end of the catheter. The contents of the syringe are then pushed inside the uterus.
Results/ Post Procedure
After the embryo transfer, the patient can resume normal daily activities. However, since ovaries may still be enlarged, the vigorous activity could cause discomfort and should be avoided.
It is best to contact the doctor if the following side effects are experienced:
About 12 days to two weeks after embryo transfer, blood test (beta-hCG) is used to detect whether the patient is pregnant.
What Are the Risks?
Ovarian Hyperstimulation Syndrome
When women undergo ovulation stimulation, they take injectable hormone medications to increase the production of eggs. The problem arises when there are too many hormones in the system which could lead to Ovarian Hyperstimulation Syndrome (OHSS). It is a condition where the ovaries become swollen and cause an immense amount of pain. The patient could experience abdominal pain, vomiting, and shortness of breath.
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.