What kind of things was he "correcting" you on? One of my biggest pet peeves is people who try to talk for me. If it made you uncomfortable, then you need to tell him. What happens if you have a valid concern you need to discuss, but then can't get a word in to your OB because your SO is too busy correcting you instead? Let him know that you're more than able to speak for yourself, that you're more than able to let the OB know the information that you consider valid and that it's offensive that he tried to talk over you in the appointment. While his opinions are also valid, there's no reason that the two of you should have to try to talk over each other to make them heard. You should go first and communicate with the OB and then ask if your SO has anything to add. And if he can't do that, then he'd no longer be welcome at any of my appointments and I'd tell him so.