I am worry about my 5 months old baby has not poo for 4 days. Should I take her to see doctor?

Babies older than 3 months who are fully breastfed may go for up to 10 or 14 days without pooping. They grow rapidly and digest practically everything they consume. This can continue until the baby is introduced to solid baby food. However, this might not apply for formula-fed babies, who should continue pooping more or less every day. I reckon it's safer to seek a doctor's advice especially if your baby seems uncomfortable or in pain. Your baby could be constipated because of milk allergies, If he or she is, the doctor will advise you to change formula or the type of food he or she is eating (if baby has started on solids).