Wait until your baby sits up steadily and holds their head well while wearing a...

https://www./parenting/when-can-a-baby-go-in-a-bike-seat-an-age-by-age-guide/

Wait until your baby sits up steadily and holds their head well while wearing a helmet, usually around 10 months. Front seats keep toddlers close, rear seats offer extra stability, and trailers work perfectly for naps