If you Google whether fresh or frozen embryos are better to use during an IVF transfer you will find an overwhelming amount of data that says frozen embryo transfers (“FET”) have better success overall. Many of the websites boast that using frozen embryos have higher success rates for pregnancies, and go on further to claim that using frozen embryos produces healthier babies with less complicated pregnancies and medications. This begs the question of how these “studies” were really conducted and what factors did they leave out that would not look so favorable with FET? Oftentimes, medical studies don’t consider every aspect and sometimes even skew the data to weigh in favor of a particular outcome depending on how the statistical data are run (what probability was applied, the sampling, variance and analysis, distribution, categorical data analysis, etc).
The success rates of a frozen embryo transfer (“FET”) cycle are nearly the same as fresh IVF cycles and have the same primary indicator for success – the maternal age at the time of embryo freezing. Many patients wait several years between the initially freeze of their embryos and attempting a subsequent FET cycle. Any patient no matter the amount of time between embryo freezing and thawing, can expect nearly the same potential for success as they experienced with the fresh IVF cycle, which the frozen embryos came from. Patients can rely on the same chances of success because frozen embryos are suspended in time and do not age. Women 37 years and younger experience success about 50% delivery rate per thaw. This rate declines as the maternal age at the time of the freeze increases.
There are some clear cut benefits to using FET over fresh embryos, including less medication and stress. Instead of stimulation medication, patients use estrogen and progesterone to thicken the lining of their uterus in preparation for the embryo transfer to allow implantation. Since the stimulation phase was done in a prior cycle, there is also no egg retrieval requiring anesthesia. Also, FET cycles can be less stressful than fresh cycles because factors like stimulation response, egg development, and embryo growth were considered during the fresh cycle. Another important benefit of an FET cycle is that it substantially reduces a woman’s risk of ovarian hyperstimulation syndrome (OHSS). There is also no surgical retrieval of eggs when using FET, thereby making the process less complex. One other potential benefit could be a lower cost since the medications can increase costs greatly during a fresh cycle, but this depends on a case by case basis. Cycles are also more predictable with fewer cycle cancellations. Patients can select the day of their transfer months in advance which will then be used to determine their cycle initiation date.
It is best to speak to your doctor about which option is best for your situation.