Question Summary:
Is the 40 days after you give birth a tradition or islamic?

Question Detail:

Is the 40 days after you give birth a tradition or islamic? 

Answer :

In the Name of Allah, the Most Gracious, the Most Merciful.
As-salāmu ‘alaykum wa-rahmatullāhi wa-barakātuh.
It is not compulsory upon women to stay in house for forty days specifically after giving birth. The tradition to remain in house after birth is due to health reasons and is not an obligation of Shari’ah.
And Allah Ta’āla Knows Best
Zakariya Memon
Student Darul Iftaa
Chatham, Canada 
Checked and Approved by,
Mufti Ebrahim Desai.
Daruliftaa.net