Nicest way to tell a friend(s) to keep some distance?

One of my good friends is the kind of girl who loves to pop in and it’s gotten worse since I go pregnant. I’m talking every day sometimes more than once she just shows up at my house unexpectedly. I’ve never liked when people just drop by without notice and especially now I’m tired and cranky. I’m feeling pretty irritable but want to approach the subject as nicely as possible how would you bring it up?