Fresh vs frozen embryos – whats the difference?

When couples undergo the process of In Vitro Fertility (IVF), they have a lot of decisions to make. One of them being whether to use fresh or frozen embryos. So, whats the difference?

In a fresh embryo cycle, women are given hormone treatments to help regulate their menstrual period, to stimulate multiple eggs and to help their eggs mature. Once the eggs are matured, they are removed and fertilised in the lab. The most developed embryos are then transferred into the uterus.

In frozen embryo cycles, the embryos have been created in a previous cycle and have undergone embryo cryopreservation. The embryos are typically stored at -196 degrees in a suspended state and do not deteriorate over time.

As cryopreservation techniques have improved over the last few years, more couples have began to freeze their embryos to later be used in IVF. When using fresh embryos in IVF, they must be implanted 2-5 days once they have been harvested whereas frozen embryos are usable for an infinite time once they are frozen.

Is there any difference in the success rate of IVF between frozen and fresh embryos?

Research published in the New England Journal of Medicine [1] studied 3000 women undergoing IVF treatment cycles to determine if fresh or frozen embryos are more likely to result in pregnancies and live births. They found that 36% of women who used frozen embryos became pregnant and 34% of these pregnancies resulted in a live birth compared to 34% of couples using fresh embryos became pregnant, 31% of which resulted in a live birth. These results show there is not a significant difference in the success rate of frozen and fresh embryos in IVF.

Further research has shown that these results do not apply to women experiencing Polycystic Ovarian Syndrome (PCOS) whereby the ovaries fail to release eggs. It has been proven that these women are more likely to get pregnant using frozen embryos.

This new research may change the minds of couples undergoing IVF into using fresh embryos as opposed to frozen. Not only is the success rate very similar but they also escape the large costs associated with storing their frozen embryos.