They would have had no children. They would have remained in a state of innocence but they would have had no joy, right? I know that sometimes teenagers bring misery, but there is also joy and rejoicing in your posterity. Well the fall was a planned event; it was a noble thing for Adam and Eve to fall, otherwise they would have remained in the garden. And they would have had no children, and we would have been in the pre-mortal existence waiting for them to do something so that they could have children so that we could become mortal. I know I was up there, chanting, eat the fruit! eat the fruit! because until that happened, they were just eating pomegranates and riding zebras and having a good time, but they needed to fall in order for the plan to take effect.
Book of Mormon Central, "How Can the Book of Mormon Strengthen Marriages and Families? (Jacob 3:7)," KnoWhy 302 (April 19, 2017).