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More about freezing all the embryos and doing frozen-thawed embryos transfers

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Today I have participated in a videoconference where some experts discussed about studies that were published in Fertility and Sterility journal, about the potential change from fresh transfers to the election of freezing all and transfer frozen embryos.

I have to admit that I was surprised about the current technology, where we can have a Journal Club Live, with 5 cameras and people from all the globe giving their opinions. Great.

One of the important fundaments to transfer frozen embryos is related with maternal and fetal health. In some studies with frozen embryo transfer, low weight at birth and preeclampsia were less frequent than in fresh transfers. These differences were seen in cycles with own eggs but not in egg donor cycles, which makes think that the difference is in the effect that the controlled ovarian hyperstimulation has on the endometrium, favoring an abnormal implantation. This was corroborated by some other studies that showed that high levels of estrogens or an early increase of progesterone were associated to changes in the endometrium, desynchronizing the endometrium and the embryo for implantation.

Still, this is not definitive because we don’t know yet the real impact of cryopreservation on embryos. Some studies suggest that freezing embryos is related with higher risk of high weight at birth. This is why frozen transfers in all the cases cannot be indicated yet; however, there are specific circumstances where it should be done, such as cases with high estradiol level, preterm elevation of progesterone or high risk of ovarian hyperstimulation syndrome.

Generalizability of these recommendations should be donde with caution. Not all the clinics  have freezing programs with good results. This is variable and depends on the technique and the experience that the embryologists have (in fact, in the videoconference, only one third of the participants reported survival rates over 75% after thawing). More experienced clinics that have been doing vitrification for several years have success rates similar to fresh cycles, but with the additional advantages mentioned above.\n\nWe feel very comfortable with vitrification, with very good results. This makes us easier the choice to pass to freeze all and transfer frozen embryos when the fresh cycle is not good enough. Even though, strong scientific evidence is sill missing to make a radical change to transfer all the cases with frozen embryos.

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Dr. Demián Glujovsky in CEGYR Buenos Aires
Viamonte 1432 - Buenos Aires Argentina
info@fertilityargentina.com

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