A Frozen Embryo Transfer is a procedure in which an egg is retrieved from a previous IVF cycle or donor. The egg is thawed and then transfers in to the uterus of the woman. The process does not involve anesthesia and is generally a painless treatment. The egg is transferred through a catheter in to the uterus of the woman for a successful pregnancy. The embryo is transferred on the 4th or 6th day of progesterone.
Cryopreservation is a procedure to preserve the organs, cells and any tissue at a very low temperature. After an IVF cycle, many patients wish to preserve egg, sperm or embryo at a temperature below zero for later use if there’s a failure in the first cycle IVF. The embryos are preserved in the initial stage similar to blastocyst (an initial structure of mammal) at a sub-temperature. The embryos are formed as a result of an IVF cycle where a male sperm and a woman’s eggs are mixed together in a laboratory and later retrieved for pregnancy attempt. Multiple embryos transfer result in twins, triplets and quadruplets. However, the infertility specialists don’t prefer to have a multi embryo attempt as it raises the chance of pregnancy complications. This is to ensure single embryo transfer and preserving the others for later use. This is a more cost-effective procedure and gives relief from frequent medications for ovulation.
The embryos are diagnosed with PGD and PGS to identify any disease in the embryos before implanting it into the uterus of the woman. Pre-implantation genetic diagnosis and Pre-implantation genetic screening are to prevent any genetic diseases or disorders from passing on to the children whereas PGS is to determine the number of chromosomes which shows the presence of aneuploidy. Post-egg retrieval; the embryo is biopsied, helping to get back results in time to do a fresh embryo transfer. If a biopsy is done on or after the fifth day, due to the complexity involved, it requires more time, and this becomes the reason for embryos under the screening process to be cryopreserved. Results can help to decide which embryos to transfer, resulting in a FET.
If you have been successful in getting pregnant through an IVF cycle, you can save embryos for later use. This will not only save your cost but provide another child as a sibling to your already born one.
Additional cycle opportunities
If your fresh embryo transfer is unsuccessful, frozen embryos from previous cycle may be used to try again without using ovarian stimulation medication or having another egg retrieval operation.
FET’s are more cost-effective
After the initial IVF treatment cycle, the following FET cycles are less heavy on the patient’s wallet. Medication and treatments both cost much lesser than a fresh embryo cycle. Lesser monitoring visits, no egg retrieval, insemination, or embryo culture also reduces the treatment cost by a great margin.
FET cycle is easier
FET cycles are easier as they do not require surgery or anesthesia for egg retrieval. Initially, estrogen injections are used to prepare the uterine lining and are administered only once every three days. Intramuscular progesterone is added later in the cycle which is a daily requirement.
OHSS has less than 1% chance of occurring but if potential warning signs are seen by a physician that the woman is at high risk for OHSS, the infertility specialist may recommend freezing of all available embryos rather than a fresh transfer. However, the embryo can later be safely transferred through FET if the possibility of OHSS decreases.
After egg retrieval and fertilization, the embryologist may biopsy each suitable embryo on fifth or sixth day of development. The infertility specialist ensures to prevent any genetic syndrome which might pass on to the children or might have different chromosomes number. Embryo freezing can also avail pre-implantation genetic screening (PGS). PGS looks for irregularities in chromosomal number e.g. trisomy 21, which causes Down’s syndrome and other such abnormalities that, may result in implantation failure or miscarriage.
Lesser chances of stillbirth, preterm birth, and low birth weight were observed in FET over the fresh embryo cycle.
Embryos transferring may result in a risk of multiple pregnancies, which come with an increased risk for both mother and child. A small risk of infection is also present. With cryopreservation, the freezing and thawing process may result in the loss of some embryos even after the screening, which might result in you losing an embryo which might have been present with a fresh transfer. FET might also increase the risk of “large for gestational age” babies.