To be honest- I have no idea:)
But thinking about it- it old be quite a challange to count every cell in our body at every stage of life- and that depends on the person too (think about some body- builders- they must have more muscle cells!).
I think the number of cells in an adult is relatively similar through most of our life- we do lose some neurons perhaps. I know it’s not a great answer, hope someone else can help you with it soon 🙂