Having sex during pregnancy

Hi! My girlfriend and I are expecting our first baby this year and we're really looking forward to it. Of course, her body changes during pregnancy, and personally, I find her only getting more beautiful. As a guy, I can imagine that pregnancy also comes with some discomforts, even in the bedroom. So I have a slightly cheeky question: What becomes absolutely unpleasant during sex in pregnancy? What feels good instead? And what should I, as a man, keep in mind now? Tips and advice are more than welcome! Greetings from an almost-dad!