Day 6 vs day 5 embryos

[GJW2018]

We will be going for our second FET in the new year and have embryos frozen from both day 5 and day 6. The day 6 ones have better gradings but have read that day 6 embryos have less successful implantation rates than day 5 but I’m not sure if this is just with fresh transfers or frozen? Very confused about which embryos to use would be good to hear about others experiences with this

[JA-fnuk Partner Nurse Fertility Network UK]

Seems freezing slow developing blastocyst increases the chance of future success as your Dr can ensure the lining is prepared for transfer - ask the Dr/nurse to explain this to you fully. Grading is not always given at some clinics but if it is good enough for freezing that is a positive sign.

Thinking of you as you prepare for your next treatment cycle - good luck

Janet

[Twiglet2]

normally our clinkc would tell us what ones they think will have the best chance and select the embryo for thawing ours have always went with our day 5s first However I don’t think we had a day 6 better grades than a day 5 so that might not be relevant 🤔 I would just go with whatever your embryology team suggest is the next best embryo to try 😘 that’s why they get paid the big bucks lol beat of luck to you! xx

[Raine2]

Hi, i am in the same position. The team at our clinic said they prefer to do day 5’s first even though our day 6 is top grade. I am going to double check when i go back next week as we are about to try our second FET x

[GJW2018]

thanks everyone, it’s interesting that they prefer day 5s even if day 6s are better graded embryos. We haven’t started the process yet just booking in an initial consultation so will be asking why for sure x

[Mudra85]

Hi, I've asked the embryologists at my clinic a couple of times about this.

My understanding is that for fresh transfers there is a big difference in implantation rates between Day 5 and Day 6 embryos. This is because by the time a Day 6 embryo is ready to transfer the endometrium would be out of sync. This is the reason why if none of your embryos get to blastocyst by Day 5 they would cancel the fresh transfer and freeze any that make it to blastocyst by Day 6, which they could then transfer later as part of a frozen embryo transfer instead.

With frozen embryo transfers, Day 5 embryos will generally be selected for transfer over Day 6 embryos. This is because Day 5 embryos are statiscally more likely to be chromosomally normal than Day 6 embryos.

However, if your embryos have been tested with PGT-A and have been confirmed to be chromosomally normal, Day 5 and Day 6 embryos have very little difference in terms of success rates if you're transferring them with a frozen embryo transfer cycle. This is because the time of embryo development and endometrial receptivity can be syncronised to maximise the chances of the embryo implanting.

In terms of what embryo you should transfer first, it's probably best if you speak to the embryology team about this. They should really be guiding this and be able to advise you which embryo you should transfer first and what the thinking is behind their decision.

Good luck!

[Ivfgotadream]

I have twins from a day 5 and day 6.

The embryology team paired them up as they looked at the 4 I had left and chose the ones which best complemented each other