A frozen embryo transfer (FET) is the move of an embryo that has been previously iced, and subsequently thawed, into the uterus. Traditionally, IVF has involved ovarian activation then egg retrieval and fertilizing of harvested eggs, then a fresh embryo transfer (ET) of an embryo into the uterus within five days of the egg retrieval procedure, also called IVF-ET. With the development of sophisticated embryo freezing and thawing methods attaining extremely high embryo survival rates, conventional IVF-ET (utilizing fresh embryos) has grown to be less frequent, providing way to the more commonly practiced FET.

Iced embryo transfer (FET) cycles have become essential aspects of the IVF process and therefore should be performed with excellent care to achieve a successful end result. Several components constitute an effective FET cycle. A proper evaluation of the uterine cavity to rule out the presence of an intracavitary lesion (such as a polyp or fibroid that may affect implantation) has to be undertaken ahead of the FET cycle. The majority of FET cycles are medicated FET cycles, where estrogen supplements is initially administered in order to build up the uterine coating (known as the endometrial echo complex below ultrasound evaluation), till an optimal density from the coating is achieved. This stage in the Dr. Eliran Mor is critical and the sort of and method of oestrogen supplements used (mouth oestrogen tablets, genital oestrogen suppositories, injectable oestrogen, subcutaneous estrogen), the dosage of estrogen, and the amount of time of oestrogen supplements are essential and must be personalized and modified to each patient based upon multiple factors, so that a responsive uterine lining is accomplished. The second stage of a medicated FET period involves progesterone supplementation, brought to secure the coating, once an optimal uterine coating has become accomplished. In medicated FET periods, progesterone is launched whilst the estrogen supplements is modified and ongoing. Like the case of oestrogen supplements, the type, dose, and path of progesterone supplementation, is essential. Generally, progesterone is introduced as intramuscular every day injections 5 times before the embryo move of a frozen-thawed embryo. Progesterone can also be administered as vaginal suppositories or a mixture of intramuscular shots and genital suppositories. The iced embryo move must timed accurately towards the initiation of progesterone supplementation in order for the FET to be successful. Estrogen and progesterone supplements is usually continued after the embryo move and through 10 weeks of gestation.

An unmedicated FET period, also referred to as an organic cycle FET, is generally carried out with no estrogen or progesterone supplementation. Instead, the oestrogen produced by a normally growing ovarian follicle, then progesterone produced right after spontaneous ovulation of this follicle; secure the implantation of a frozen-thawed embryo, if the FET is timed correctly for the time of ovulation. Natural cycle FETs do not allow for flexibility within the timing in the FET and therefore are only appropriate for patients with normal menstruation periods, in which ovulation is not hard to monitor and is foreseeable.

In certain clinical scenarios, a stimulated FET period is conducted. Inside a activated FET period the patient administers gonadotropin hormonal shots (or oral ovulation induction medications) to cause the development of the follicle or follicles. The expansion of hair follicles leads for the endogenous manufacture of estrogen which then leads to the thickening from the uterine coating. As soon as follicles reach a mature size, these are brought on to ovulate, leading to producing endogenous progesterone, which then units the phase for that embryo move of a frozen-thawed embryo. Stimulated FET periods may be applied in patients who do not ovulate naturally or in instances where conventional medicated FET cycles have been unsuccessful.

Iced embryo transfer periods permit excellent versatility in optimisation in the uterine lining just before thawing of embryos, so that embryos are not thawed till the uterine coating is receptive. The fundamental contributor required to achieve an optimally nrrbzz and responsive uterine coating, is oestrogen. In cases of the insufficient uterine lining throughout an FET period, in addition to variations in the type of estrogen medication, dose, and route of administration, a few other health supplements can be added to enhance the coating thickness (including baby aspirin, pentoxifylline, vitamin E, Viagra, G-CSF…).

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