Regardless of your baby’s birth weight, resist the urge to stock up on newborn sizes. Babies grow quickly at that age, says Dr. Resnick, and your baby will be a size 1 before you know it.

Whether you're stocking up before baby arrives, making sure you have the right fit, or packing for vacation, our diaper size chart will help you plan.

When to Worry If your child's growth rate slows down (weight, height, or head size) and she falls below two percentile lines, then you should explore the reason for the poor growth.