"刚学步的小孩" can be translated into English as "a toddler" or "a baby who is just learning to walk".
"Toddler" is a common and concise term used to describe a young child who is learning to walk, typically between the ages of one and three.
The longer phrase "a baby who is just learning to walk" provides a more literal and descriptive translation, suitable for contexts where clarity is paramount.
In most casual or general contexts, "a toddler" would be the preferred choice.