Will someone talk me through numbers?

[Jazper]

Hi all ☺️
Just done my first round of IVF and finished my OHSS monitoring today after having had 31 eggs collected. Of those 31 eggs, 27 were mature and 23 fertilised. 6 have made it to blast and are on ice with another 1 being given an extra day to develop. I await an update tomorrow on this. While I do not have the grading of the embryo's yet, I am obviously really happy that I have 6 that were deemed 'good enough' to freeze.
I will of course ask the embryologist tomorrow but I'm curious, what could have caused such a huge drop between fertilisation and blast stage? Is it reasonable to suggest that if I had collected fewer eggs, I would have less blasts right now? Or is this not how it works?
I'd be super grateful for any suggested questions to ask the embryologist tomorrow too. Many thanks in advance

I'm pretty sure I read a study once that showed there was an "optimum" number of eggs to collect - too low then risk too few blastocysts and too high then quality is adversely affected and also reduced blastocyst numbers

Most women I know who had OHSS had a worse number of blastocysts or the same as women who didn't

6 is still an amazing number - most clinics whilst they say they aim to get as many as possible what they mean is eggs not blastocysts - what they don't publicise is that really they often expect women to get just 1 blastocyst to transfer and possibly 1 to freeze and that's it

@snowdropsanddaffodils the 'optimal number' is 15, but not because the chances of success drop off higher than that, but because they level out (and in the meantime risk of OHSS starts to skyrocket) :)

I agree with others, aiming for 12-15 eggs is best, with larger amounts the high drop off you've had happen is pretty common. 6 is excellent and whether you had 12 eggs collected or 31, the outcome of 6 is great.

Really appreciate your comments. Thank you so much. I hope I don't sound ungrateful. I feel incredibly lucky to have the number of blasts I do. I won't lie, the big drop did surprise me and made me a little concerned about the quality of my eggs in general but you've all explained it well, so thanks again. Here's hoping for some good grading and a successful transfer.

Very common @Jazper - my DP had 28 collected and ended up with 5 blasts. As soon as you hit OHSS levels you run a risk of big drop off. I had a round where I had 28 collected and ended up with 2 blasts. I had a round with 14 collected and got 7 blasts. Anything over about 20 is too many really.

Great results though, so congratulations. Wishing you the best of luck when you have your transfer. The first of my DP’s FET (she also couldn’t have fresh) is now asleep in my arms, so hopefully it will be equally as good for you.

Great results, but indeed it's a big drop. Keeping everything crossed that they will rate highly. x

@Jazper,
From my clinic’s website: “We are aiming for 8 to 10 eggs per attempt, which gives an optimal chance of good embryos and therefore a pregnancy”.

6 blasto is in any case excellent, congratulations!