Morula FET

[Persuing Lacey]

Hi Carole,

I am hoping you may be able to help me. I currently have a day 5 normal XX GSN morula to be transferred my next FET. Can you please tell me what you prefer, 1 - an immediate thaw and transfer, or 2 - growing the embie to blast and then transfer. Plus your reasons why.

Any help you can offer is much appreciated.

[Carole]

Hi Carole,

I am hoping you may be able to help me. I currently have a day 5 normal XX GSN morula to be transferred my next FET. Can you please tell me what you prefer, 1 - an immediate thaw and transfer, or 2 - growing the embie to blast and then transfer. Plus your reasons why.

Any help you can offer is much appreciated.

Hi Lacey,

A day 5 embryo is already at blastocyst stage or real close so extended culture will not be helpful to you. In fact, pregnancy rate from day 6 embryos are frequently reported to be lower and day 7 embryos have very poor pregnancy rates. Extended culture to blast allows selection of the best growers among a group. Since only one embryo is under consideration for transfer, you don't have any reason to apply selection pressure to a group. So I would thaw and transfer. You will know in approximately 2 weeks whether the embryo grew and implanted if you are pregnant. Good Luck!! Carole

[Persuing Lacey]

Thank you Carole. Could you offer an explanation as to why a normal healthy embryo might be so far behind? And in your experience what is morula pregnancy rate for a chromosomly normal embryo. Thank you.

[Carole]

Thank you Carole. Could you offer an explanation as to why a normal healthy embryo might be so far behind? And in your experience what is morula pregnancy rate for a chromosomly normal embryo. Thank you.

Hi Pursuing Lacey,
Normal progression depends on several factors. Chromosomal abnormalities (depending on the type) may or may not hinder progression. For instance, Trisomy 21 is a chromosomal abnormality but does not hinder embryo development--we know that because many children with Downs syndrome (caused by Trisomy 21) are born every year. Other chromosomal abnormalities do not permit development to more advanced embryonic stages, let alone to birth. So the type and severity of chromosomal abnormality is important.

On the other hand, even a genetically normal embryo may have other issues that prevent normal development. For instance, the powerhouses of the cell, called mitochondria, are inherited through the egg. Some eggs have few in number or somehow weaker mitochondria, causing the embryo to fail to progress. The cytoplasm from younger women containing mitochondria have been injected into eggs from older women and increased pregnancy rates have been reported. These mitrochondrial injection studies were stopped by the FDA because mitochondria contain DNA, thus introducing DNA from a third "parent" in embryos produced via this method. There may be other reasons that we don't understand for poor embryo development but at least these two (aneuploidy and weak mitrochondria) are known factors.

In my experience, morulas on day 4 of culture are perfectly fine and on target as far as progression- I would expect a good preg rate. Morulas on day 5 (early) may also be fine but I might expect a slightly lower pregnancy rate with any embryo that is progressing more slowly.Regarding actual rates, you should ask your clinic for their experience as that is most relevant to your situation. Hope this helps. Good Luck!! Carole

[Persuing Lacey]

Thank you Carole, all very interesting!