I have an Ergo, but I don't have the newborn insert. Does the insert work? Is it worth buying one? Or do babies get too hot in Singapore?

Yup like what Sam mentioned, you need the insert if they below 4 months of when their neck is not strong to support on their own. However, I feel the insert is a waste of money because I bought 1 together with the Ergo but used it like 1-2 times only.