Things are not amicable between Megan Fox and Machine Gun Kelly as she gets closer to giving birth to their baby ... and the lines of communication are closed.

Sources familiar with the situation tell TMZ … Megan and MGK are not on good terms and things are so bad they aren't even speaking to each other.

Megan is due to give birth in March, but we're told her relationship with MGK is so icy it's unclear how involved he will be when the baby comes.

Our sources say Megan seems to be done with MGK and everyone in her orbit is happy about it ... they feel like she finally came to her senses by shutting him out of her life.

TMZ broke the story ... Megan and MGK called it quits during their Thanksgiving trip to Colorado after she found some upsetting material on his cell phone. We're told the stuff she saw was "relationship ending."

Unclear what will happen with MGK when Megan goes into labor, but we're told she doesn't  want anything to do with him.

Stay tuned ...