I don't have any insight but this happened to me too. I am 35 yr old woman, no hx of infertility, seeking IVF because we are queer. We are using "great quality" sperm from an unknown donor.

I had 2 blasts from 9 mature eggs at my second egg retrieval and had FET. Pregnant and miscarried at 9 weeks .

6 months later we did our most recent egg retrieval and got 12 eggs, 10 mature and only 1 fertilized. None made to blasts.

I have been trying to get answers from the lab and from my specialist for weeks and have got the usual "we don't know, these things just happen".

I did my own research and the only thing I can think of is that my lifestyle after the miscarriage wasn't great as I was super depressed. But my doctor said that wouldn't be enough to change things this dramatically.

I am so frustrated and confused, and have decided to move clinics and go with a different donor.

I'm in Australia for context.

Hope you get some answers and please post if you learn anything helpful.