Wait until your baby has strong head control and sits up on their own before...

https://wiki-velo.win/index.php/The_Compatibility_Conundrum:_What_To_Do_When_Your_Child_Bike_Seat_Doesn%E2%80%99t_Fit_Your_Frame

Wait until your baby has strong head control and sits up on their own before hitting the trail. Whether you are looking at a rear seat or a trailer, I have broken down what to watch for. Let’s ensure your little passenger is ready for the ride.