Scylla is right. There is no automatic renewal because of your baby.
If you want to keep your PR, you should stay in Canada this time. If you are now in Canada, you can stay for 2 years without leaving, even if your PR card expires in the meantime. After two years, you can renew it again because you meet the requirements again. After that, you can leave Canada again for up to 3 years but then you must return again to stay another 2. Or you could stay 3 years and apply for citizenship.
If you are hoping that your child will sponsor you again when they turn 18, this is not a very safe bet. At 18, your child may have other ideas about what they want to do with their life. Even if they do want to sponsor you, it is not that easy. They have to move to Canada, they need a decent job to show that they have income to sponsor you which means they first need education. Sponsorship of parents takes years so by that time, your child may have a family of their own which means they also have to make enough money to support their family as well as their parents. You see it is not that easy.
