Those arrested were identified as Ravi Aalekar (40), his wife Vaishali (35), Vinita Bais (36) and Suman Sharma (60), Additional Superintendent of Police (ASP) Bittu Sahgal told reporters here.
Vinita and Suman had allegedly stolen the baby, Vivek Dholi, from Maharaja Yeshwantrao Hospital yesterday, he said.
The two had engaged the infant's mother, Mamta, in a conversation and sent her to have tea. When she went outside, they picked up the child and fled from the spot, he said.
Sahgal said they are probing the role of a sadhu (seer), who is suspected to have facilitated the sale of the child.
This is the second incident in which a child has been stolen from M Y hospital in the last 40 days. On February 25, a baby was stolen 20 minutes after he was born. The infant was found with a school teacher on March 1.
According to the ASP, hospital staffers are also under scanner in connection with both these incidents.