Well there are a few thngs to think about here. Was he up until that time a reasonable man and just suddenly upped and went as if he could not cope with pregnancy etc. Not that it excuses his behaviour in any way just wondering what sort of man he was before then. What I am getting at is have you any reason to suspect he will cause disruption other than the fact that your partner may not like your ex looming. The fact is, that he is the father and I think you will have to go along with it, for her sake as well, just in case he really has grown up and had a change of heart and wants a genuine relationship with her, which could in turn enrich her life and who knows, give you a break in the future from time to time. If he is a complete monster then obviously you can make it difficult for him, but I think he needs to be able to have a chance, although I can understand your concerns. Its hard to see how to start it though if you want to be present, either that means you have to be on your own with him and her, or your partner will be there too, all of which could be a bit tense! Maybe you could have a long chat with him first and explain it just like you have here, after all, if he genuinely has her interests at heart he will go along with whatever you suggest hopefully. Just an afterthough, has he got a new woman in his life ? Maybe that has precipitated the renewed interest.