I don't think the Fruit of Abundance has anything to do with fertility (but I could be wrong) I think it just gives you the chance to gain skill points in all of the skills plus a few you can't get by eating the other fruits.
I've just finished a test where I had my Sim gain skill points by just eating the fruit from the tree. When he ate a fruit, it gave him one of the skills from that set (as listed before) If any of the skills in that set were maxed, it just gave the skills he needed eg when he had maxed cooking and ate from the Fruit of Harvest, he only got fishing or gardening. And when he had maxed all of those skills, there was no effect when he ate the Fruit of Harvest after that.
By maxing all these skills (he had 35 trees to pick) when a yellow tree did appear, there were less options for what skills he would gain. Eventually when eating the Fruit of Abundance, he gained points in Mixology, Nectar Making, Piano, Drums and Bass.