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Frozen Embryo transfer (FET) is when leftover frozen embryos from a previous IVF cycle are transferred to you during a natural or medicated cycle.

Should I freeze my leftover leftover embryos?
If you have any embryos leftover after your fresh IVF transfer, you may want to consider freezing them. Some of the reasons to consider freezing your embryos are: it is a lot less invasive and involves fewer drugs (sometimes none) than an IVF cycle. It is also less expensive than an IVF cycle because it involves fewer procedures. While FET success rates are usually not quite as high as IVF success rates, many women have become pregnant during their FET cycles. In 1996, the Center for Disease Control and Prevention (CDC) reported that for women under 35, 18.2% of FETs resulted in live births, compared to 28.7% for fresh IVF cycles. More statistics, statistics for individual clinics, and statistics for different age groups can be found at the CDC web site. Make sure you find out what your clinic's embryo thaw rates and live birth rates are for FET. You should also find out the prices for freezing, storage and the actual FET procedure, before you make your decision.

What is the difference between a natural cycle and a medicated FET?
During a natural cycle FET, your natural cycle is monitored to determine the correct timing to transfer the embryos. During a medicated FET you are given medications (Sometimes Lupron, usually some form of Estrogen and then after transfer some form of Progesterone) to create an artificial cycle in which the clinic has more control over when to transfer the embryos.

A Natural Cycle FET Experience
I opted to do a natural cycle FET, since my clinic had been experiencing a better success rate with their natural cycle FETs. A natural cycle at my clinic does not require any medications. Three days after my period started I had to go in for my first blood work. They measured my FSH level to make sure it was below 10. My level came back at 7. The blood work monitoring for my cycle was to begin at day 10. I was to go in for blood monitoring each morning until my LH level had surged. Each day the lab measured my E2 level and my LH level. Here is what my levels were like:
 

	Day 10	Day 11	Day 12	Day 13	Day 14	Day 15
LH	8	8	8	8	15	55
E2*	309	227	352	738	839	856

*Please note that these E2 levels are in Canadian measurements (Picomols).

Since this was a non-medicated cycle, the clinic wanted to see my E2 level between 600-1000* for the one mature follicle I would likely be producing. I was kind of surprised when my E2 number went down after the first day. The nurse told me that they weren't concerned since there was a margin of error when testing the E2 level and that my number may not actually have gone down. They wanted to see the LH number surge to at least triple what it was to begin with (somewhere above 30). Once my LH had surged they would schedule my transfer for 3 days later. The reasoning behind transferring the embryos 3 days after my surge was that during a normal cycle the embryos wouldn't make it to the uterus until a few days after the LH surge. I surged on day 15. The afternoon before my transfer my embryos were thawed one at a time, until there were 3 viable embryos available for transfer. The next morning 3 of my embryos were transferred to me (3 days after my LH surge). -- Brenda

Will all of my frozen embryos survive the freeze/thaw process?
It is difficult to say if all of your embryos will survive the freeze/thaw process. I have seen thaw rates ranging anywhere from 50-95%. Some clinics are being more selective about the embryos that they transfer, in order to get a better thaw rate. Of course this rate may include some people who had a 100% thaw rate and others who had a 0% thaw rate. "My clinic's thaw rate was around 50%. The lab technicians had to thaw 8 of my frozen embryos to get 3 viable embryos for transfer. This means I only had a 38% thaw rate." -- Brenda. Ask your clinic how many frozen embryo transfers they did in the previous year and what their thaw rate was during this time.