Egg retrieval results

MJ

I had 15 eggs retrieved yesterday and found out only 7 fertilized! How can this be, that's less than 50%! My last ER I had 15 and 14 fertilized but only 1 made it to day 6. Neither my husband or I have fertility problems. I just don't understand our outcome. Now we have to wait for genetic testing. What are the odds of the 7 making it to day 5 and being "normal"?

Any stories/thoughts would be appreciated