Meanwhile, the older they get, the harder it is for them to conceive naturally. So, the chances of 35-year-olds for successful fertilization are about 20 (!) times lower than those of 20-year-olds. And by the age of 40, the chances are already 40 times lower. Therefore, doctors say that you should not delay the birth of your first child. In addition, the older a woman becomes, the more likely she is to have a baby with chromosomal abnormalities, primarily Down syndrome.