Chromosomal abnormalities in eggs can lead to miscarriage.

“And as a consequence, there are multiple chromosomes or duplications of chromosomes, things like trisomies. Sometimes too many chromosomes move away and there are actually removal of entire chromosomes, meaning both strands, so that you have chromosomal deletions. And in that case, typically fertilization won't occur. But there are instances in which fertilization will occur. So a woman will get a positive pregnancy test. Her periods will stop. And the couple will think that they're advancing along the steps to a successful pregnancy, and then there will be, sadly, a miscarriage.”