Is taking bird nest during pregnancy necessary? Is it scientifically proven that it helps mum and the newborn.

If you wanna look at it from science perspective, nothing from TCM is ever truly proven scientifically! It's more of a belief over traditional medicine, or in this case, the belief that bird's nest will help one way or another - it's up to you whether you'd want to take it a not, and same goes for anything else recommended at any point of time. What I would say is I don't really see much benefit over eating/drinking a bird's saliva but ... It's all up to personal preference!