My baby 50 days old and have caught cold. will this affect her brain growth or her health by any way..?

No!: Colds are extremely common in children of all ages. In a baby who is 50 days old, a cold will most likely cause a runny nose, cough, and even perhaps a mild fever. A simple cold in no way will affect her brain or her growth.

Not likely: At 7 wks the more common reason for a stuffy nose would be airborn irritants (perfumes, smoke, house dust, etc.) but a 7wk old could get a cold. Most of these are limited to the upper airway though they occasionally affect the lungs. As long as your baby is feeding well enough to remain alert & interactive, wetting diapers every 4-6 hours & playful much of the time, i would not worry.