Frozen Embryo Transfer Cycles

Transfer of the cryopreserved embryos may be performed in a natural cycle or in a hormone-supported cycle. The number of embryos to be transferred depends on the age of the woman and the condition of the embryos, in addition to the experience in past treatment cycles. If the embryos were frozen at cleaved stage or blastocyst, they can be thawed and replaced in the same day. However, if they were frozen at the two-cell pronuclear stage of development, they are thawed one to two days before and cultured to allow them to divide and are replaced when they develop further.

There is the possibility that embryos (some or all) will not survive the freeze/thaw process. Therefore, it may be necessary to thaw out several embryos to get two or three good embryos for the transfer. The chance of conceiving and delivering a child after transferring cryopreserved embryos depends on several factors specific to the patient. These include the number and quality of the embryos transferred and the age of the woman. Typically, the average pregnancy and delivery rates of cryopreservation cycles are lower than the average rates of fresh cycles.

Natural Cycle

This can be done in women with regular menstrual cycles. It involves serial ultrasound scans to check the development of the follicle and endometrium, blood tests to check the levels of hormone LH, estrogen and progesterone. Embryo transfer is usually performed about 3-5 days after the LH surge (2-4 days after ovulation). The woman takes medications starting as early as the day after ovulation or the day of embryo transfer. Typically, progesterone started on or before embryo transfer will be continued throughout the luteal phase. Natural cycles have the advantages of a naturally prepared endometrium and reduced cost. The disadvantages of natural cycle frozen embryo transfer is the risk of failure of ovulation, improper timing of the cycle, or underdevelopment of the endometrium.

Hormone Replacement Cycle

This involves giving estrogen in the form of tablets, injections or skin patches and later adds progesterone in the form of tablets, suppositories or injection. After embryo transfer, both estrogen and progesterone are continued until the pregnancy test. In the test is positive, the woman should continue the medication for a further 8-10 weeks. Hormone replacement cycle allows accurate programming the date of embryo transfer and ensures that the endometrium is adequately prepared to receive the embryos. Therefore, at Laurel Fertility Care, we recommend hormone replacement cycles for our patients undergoing frozen embryo transfers.

Frozen embryo transfers result in a lower pregnancy and live birth rates than fresh embryo transfers. However, there is no difference in the pregnancy rates for a frozen embryos transfer after a natural or a hormone replacement cycle. The success rates depend on many factors including the age the woman providing the eggs, the quality and number of embryos transferred. The outcome of pregnancies resulted from frozen embryo transfer is similar to fresh embryo transfer in the incidence of biochemical pregnancy, blighted ovum, early and late miscarriage , preterm deliveries and term deliveries.