Are frozen embryo transfer (FET) success rates higher than fresh transfers?
It is quite common for patients to ask if a frozen embryo transfer (FET) is likely to be more successful than a fresh embryo transfer.
In medical literature, studies have shown that frozen embryo transfers (FET) were giving higher pregnancy rates. But after that data was stratified and analyzed further, it seems as though there's a select patient population that will benefit from FET. One group are hyper-responders (or high responders). These are patients on medication who produce lots of follicles that are going to produce a lot of eggs. All of those follicles make a lot of estrogen and the high levels of estrogen seem to have a little bit of a negative impact on embryo implantation at the lining of the uterus or the endometrium, resulting in lower pregnancy rates.
For women who are hyper-responders, a freeze-all cycle is recommended for two reasons:
- To improve the implantation rate
- To reduce the risk of ovarian hyperstimulation syndrome (OHSS), a rare condition where you actually can get sick from having so many cysts on the ovaries developing and hospitalization is sometimes required.
Other situations where patients are likely to benefit from FET:
- Patients who develop fluid in the lining of the uterus. This can happen from blocked swollen tubes, from polycystic ovarian syndrome (PCOS), a prior cesarean section called an isthmocele, where fluid can seep up into the endometrium and will reduce implantation.
- Patients with rising progesterone levels as this can have an effect on the lining of the uterus.
- Patients with multiple unsuccessful fresh transfers.
So what's the bottom line here? Is frozen for all? Absolutely not—only a select patient population will benefit from frozen. Fresh is still an excellent opportunity that also reduces the cost of having to have another frozen cycle. Fresh and frozen are essentially equivalent, but in certain circumstances for select patients, frozen will be better.
Who is that for? Hyper-responders, patients who have fluid in the lining, patients with elevated progesterone, patients where there is a concern about hyperstimulation or patients with multiple unsuccessful fresh transfers.
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