If your child is under 6 months old, a reclining seat is a very important feature. Since infants often cannot hold up their own head until 3-6 months of age, they need a seat that reclines in order to properly support their head. Doctors also recommend that infants under 3 months old lie flat in order to allow for proper spinal alignment, freedom of movement and so that they may turn their heads if they need to spit up.