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Embryo freezing

Details frozen embryo replacement.


How can frozen embryos be replaced?

Frozen/thawed embryos may be transferred into the uterus in a natural cycle, a hormone replacement cycle or a stimulated cycle. In general, the three methods have similar pregnancy and live birth rates.

Natural cycle (without any drugs)

This is usually recommended in young women with regular menstrual cycles and ovulation. 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 3-4 days after the LH surge (2-3 days after ovulation). The woman is given no drugs until the day of embryo transfer. On the day of embryo transfer, the woman may start a course of progesterone pessaries or tablets to support 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. Also,. the date of ovulation can not be predicted.

Hormone replacement cycle with or without GnRh agonist

This is usually recommended for older women, woman without ovaries or non-functioning ovaries, women with irregular infrequent menstrual cycles or ovulation. It involves giving estrogen in the form of tablets or skin batches and later adds progesterone in the form of tablets, pessaries, gel or injection. Different IVF clinics have different protocols for giving these medications and in some women GnRh agonists may be given in addition to hormone replacement to "switch off" any hormone production by the ovaries which may interfere with the treatment. 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 programng the date of embryo transfer and ensures that the endometrium is adequately prepared to receive the embryos.

Stimulated cycle

This is where fertility drugs such as clomid tablets or FSH injection is given aiming to produce one or two follicles. When the follicle is mature and the endometrium developed satisfactorily, hCG injection is given to induce ovulation. Embryo transfer is usually performed 2-3 days after the ovulation. This regimen is usually recommended for women do not ovulate regularly and did not respond to hormone replacement treatment in a previous cycle.

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