you have a 15 to 20 percent chance born with 1 to 2 million eggs your supply dwindles to 300,000 Parents.com One estimate puts it at 90 percent your most fertile years your most fertile years your supply dwindles to 300,000 you have a 15 to 20 percent chance born with 1 to 2 million eggs women in their mid-thirties and beyond odds of having a miscarriage ninety percent of a woman’s eggs are chromosomally abnormal use eggs donated by a younger woman prime time for fertility chromosomal abnormality