Mumbai blood group classification and blood transfusion precautions Mumbai is one of the most populous cities in India, where people of all blood types are found. It is critical to understand which blood transfusions should be received by people with different blood types, and what to pay attention to during the transfusion process. This article will introduce in detail the blood type classification and blood transfusion precautions in Mumbai from aspects such as blood type classification, blood type transfusion principles, blood transfusion for pregnant women and blood transfusion complications. 1. Blood type classification Currently, there are four known blood types: A, B, AB and O, among which the ABO blood group system is the most basic.