IVF, or in vitro fertilization, is the process of bringing together a sperm and an egg, outside of the body (in the laboratory). This is compared to in vivo fertilization (natural conception), where the egg and sperm come together inside the body.
While in vivo fertilization (natural conception) only involves 1 egg, in vitro (IVF) is usually performed with multiple eggs. In fact, most women take medication for approximately 2 weeks to stimulate their ovaries to produce anywhere from 2- 40 eggs. The purpose of this multi-egg stimulation is to improve the chance for conception.
In the early days of IVF, multi egg stimulation was critically important because once an egg was removed from the ovary, the likelihood of that egg becoming fertilized and growing was relatively unreliable. Further, the success rate of any embryo actually becoming a baby was also relatively low. Therefore, if one could procure multiple eggs, there was a greater chance that at least one embryo would become a baby.
As the efficiency of IVF improved, patients and doctors found themselves with more embryos available than were needed to transfer into the uterus. Instead of wasting or discarding these “extra” embryos, they were frozen for future use. By convention, these “extra” embryos were usually lower quality than the embryos which were transferred into the uterus. Non-coincidentally, the success rate when these embryos were subsequently used was lower. Therefore, when one compared the success rates of fresh to frozen IVF, the fresh was superior.
Over the last few years, our technique of freezing embryos has improved dramatically. A process called vitrification, or flash freezing, has made egg freezing possible. This same technology has been applied to embryo freezing with wonderful results. With this improvement doctors can now freeze embryos for other reasons than simply having “leftovers”. Indications such as hyperstimulation syndrome (OHSS), fertility preservation, embryo “banking” prior to PGD and other reasons have demonstrated that when top quality embryos are frozen, they have as good success as fresh embryos. In fact, some recent research suggests that, in some situations, frozen embryos may actually be better than fresh embryos!
Thus, when considering fresh vs. frozen there really may not be reason to fuss.
If you have questions about embryo freezing or fertility treatments in general, feel free to contact us, we’d be happy to speak with you.