Both of my 4month old twin babies are putting fingers in their mouth and inducing vomit a number of times. What does this signify and how can I stop it?

Red Nose does not have any specific information about this nor is it a part of Safe Sleep recommendations.

Have you chatted with your Maternal Child Family Health Nurse or GP/Paediatrician about this?
What State are you from? - I may be able to provide you with contact services within your State.