Most doctors recommend waiting until your baby hits nine to twelve months old...

https://wiki-tonic.win/index.php/Do_I_Need_to_Avoid_Curbs_with_a_Baby_in_a_Bike_Seat%3F_The_Mechanic%E2%80%99s_Guide_to_Smooth_Riding

Most doctors recommend waiting until your baby hits nine to twelve months old before hitting the trail. You need to ensure your little one can sit up confidently without support and hold their head steady while wearing a helmet