Most experts suggest waiting until one year old. Your child needs strong neck...

https://www.sierrabookmarking.win/wait-until-your-baby-turns-one-they-need-steady-head-control-and-the-ability

Most experts suggest waiting until one year old. Your child needs strong neck control to wear a helmet while sitting upright. If they sit unassisted, they are ready. Front seats offer engagement and rear seats provide stability