IVF is a fertility treatment in which eggs are fertilized by sperm in the lab. The fertilized eggs grow in special incubators to the point where they have enough cells to be transferred to the potential mother’s uterus.
In the initial IVF cycle after the woman’s ovaries have been stimulated to produce extra eggs, fresh embryos are transferred. If there are more embryos than needed for this cycle, the extras are frozen for use in future IVF cycles.
For many years, the prevailing wisdom in assisted reproductive technology (ART) has been that fresh embryo transfers are more successful than frozen embryo transfers (FETs), when FETs are thawed and transferred to a woman’s uterus. The thinking was that the best quality embryos would be selected for the fresh cycle to increase its chance of success, and that the remaining embryos, while still good quality, might not be as optimal as the ones used in the fresh cycle.
Current data implies that this perception may need to change. The most recent information reported to SART, the Society for Assisted Reproductive Technology, for 2013, shows that for women 35 and over the percentage of transfers resulting in live births is actually higher for FETs than for fresh embryo transfers. What seems to matter most to success rates is the mother’s age at the time the embryos were frozen, rather than her age at the time of transfer.
There haven’t been any research studies yet to determine why FETs are becoming more successful or if the procedure for IVF should change to using FETs exclusively. So if you are going for IVF, your first cycle will be a fresh one. If you need a second cycle and you have frozen embryos in storage, you will receive FETs. There are advantages and disadvantages to each.
Pros and Cons of Fresh Cycles
In a fresh cycle, a woman has to have hormone treatment to regulate her menstrual period, stimulate multiple eggs to develop (superovulation), and help the eggs to mature. You have to be monitored carefully during this time. When the eggs are mature, they are harvested and fertilized with sperm in the lab. Two to five days after harvesting, the embryos which have developed the best are transferred into your uterus. Fresh cycles have been used for decades in IVF treatment and have a long history of success. Another advantage is that, if you are successful with your first, fresh cycle you don’t have to go through the intensive hormone injection treatment again unless you want to have another child later on and use your frozen embryos. The medications used for this treatment are much less intensive (and expensive!)
The fertility medications are demanding of your body. Higher levels of the hormone medications are required for ovarian stimulation than are needed when FETs are transferred. Fertility medication costs for your fresh IVF cycles may range from $4,500 to as much as $10,000. Just to be clear, however, remember that you can’t have a frozen cycle without first going through ovarian stimulation and the whole laboratory procedure to develop embryos, whether you are going to use them fresh or frozen.
Pros and Cons of Frozen Cycles
When you have a frozen cycle, you don’t have to go through ovarian stimulation or egg retrieval, since you did that in an earlier fresh cycle. You do have to use estrogen and progesterone to thicken the uterine lining and prepare it to receive the embryo transfer, but these medications are much less expensive than the ovarian stimulation medications. They also have fewer potential side effects, are less demanding of your body, and the ultrasound and bloodwork monitoring that the practice does for you is not part of the FET protocol.
Many people find that FETs are less stressful than fresh cycles because they don’t have to worry about egg production or if there will be viable embryos, since those procedures have already been done. Another advantage of a FET cycle is that you can schedule the date of the transfer months in advance and plan for it.
Your chances of success with a FET are about the same as they were when the embryos were first frozen, because freezing keeps them from aging. Recent data for transfers suggests that FETs may be more successful than fresh cycles for women 35 and over, but studies have not yet been done to validate this.