Start biking once your baby sits well unsupported and holds their head steady...

https://high-wiki.win/index.php/Is_It_Safe_to_Bike_With_a_Baby_If_They_Were_Born_Premature%3F

Start biking once your baby sits well unsupported and holds their head steady in a helmet, usually around age one. Choose a front seat for bonding, a rear seat for growth, or a trailer for extra stability. Keep your first rides short and fun.