There are millions of couples going through IVF that fail to get viable embryos. Probably 3/4 of women over 40 fail to get any successful pregnancies, and many younger ones too.
Depends how much over 40. "At age 40: 44% will have a conception ending in a live birth within one year, 64% will have a conception ending in a live birth within four years" https://en.wikipedia.org/wiki/Age_and_female_fertility