In the event there are more embryos surviving than are needed at the time of transfer surplus embryos are frozen, or cryopreserved, for later transfer. The frozen embryo transfer (FET) process does not involve taking injectable gonadotropins. Coordinating the frozen embryo transfer can be done with or without medications. Cryopreservation allows for attempts at achieving pregnancy without the high-cost of a repeat IVF cycle.
It is a technique involving the removal of a small portion of the zona pellucida (outer layer of the oocyte or early embryo). This process is done prior to transfer. Age is the predominant determining factor for using assisted hatching. Assisted hatching is considered on an individual basis.
There are multiple risks involved with the medications and retrieval process. A brief summary is provided here. Patient should have a full understanding of these risks and ask questions regarding these risks prior to signing the consent forms.
Ovarian Hyperstimulation Syndrome(OHSS):
This is a combination of symptoms that result from the elevated levels of hormones and other factors that result from excessive stimulation of the ovaries. It can be predicted beforehand and can be prevented by adopting a number of strategies. In spite of preventing measures severe symptoms like ascitis, respiratory distress and other complications may develop. In that event cycle is cancelled, embryo transfer is deferred and kept frozen. Sometimes in severe cases ICU support may needed.
The use of medications to stimulate increased numbers of follicles will also increase the rate of multiple pregnancies. Up to 20 percent of pregnancies conceived while taking gonadotropins will be multiple gestations. Most of these will be twins, however, triplets and higher numbers of gestations are seen as well. This is in contrast to the one to two percent risk of multiple gestations in the general population.
Ectopic pregnancies (tubal):
There is a very small increase in the incidence of ectopic pregnancies due to gonadotropins. The risk of ectopic pregnancy is not eliminated by IVF, though it is very uncommon.
With ovarian stimulation from gonadotropins., the size of ovaries is increased. This increase in size can lead to a twisting of the ovaries which interrupts the blood supply. Surgery is often required to alleviate the problem. Torsion occurs in less than 1% of patients.
There is much debate about relation of ovulation inducing agents with a woman's risk for ovarian cancer. The risk of ovarian cancer does have a correlation with the number of times a woman ovulates. Pregnancy and breast feeding has been shown to decrease the risk of breast cancer as do birth control pills.
The retrieval process involves the passage of a needle into the abdominal cavity through the vagina. There is a risk of infection as a result of the oocyte retrieval. Prophylactic antibiotics are used to help prevent infections. The actual incidence of peritonitis is exceedingly rare.
Perforation and haemorrhage:
Injury to intra-abdominal organs and vessels is always a concern during the retrieval process. Organs at risk include the bowel, bladder, and vessels. Because the needle is relatively small this complication is not as common as one would expect. Keep in mind needles are used to puncture vessels in order to draw blood. Punctures of intra-abdominal organs likely seal themselves in a similar fashion.
Following the procedure someone may experience a moderate amount of abdominal discomfort due to enlarged ovaries and manipulation from the procedure.
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