My 9 month old height and weight ?

How to fatten baby up a bit ?

He is in the 8% tallest centile but bottom 20% for weight 🤷🏻‍♀️

Nurse said genetics can play a role and on my side of the family men are quite tall and slender but I'm still worried. He is thriving and full of energy but literally slender like a long little meerkat lol