How can women know they are pregnant just by holding their breast?

Question

I’ve seen this scene in movies and tv shows many times, like ‘Mother’, ‘Peaky Blinders’ and so on. They just hold a boob, it can be their own or another woman’s, and go “oh, I’m/you’re pregnant”. What exactly are they feeling when they do this?

In: Biology

Answer 1

Think when they hold theyr own boob it can be because of sensitivity, and areolas grow darker. But dont know how they would know by touching breasts of another woman.