How was this avoidable, whoneedssleepanyway ?
He was over the moon - they obviously continued with the pregnancy - he then changed his mind once the pregnancy was fairly advanced. I presume a lot of discussion on the baby was had from the moment they found out OP was pregnant and it is only NOW that he is not 'over the moon' anymore.
If the baby was unplanned, a more mature person would presumably have done their hard thinking in the very early weeks of the pregnancy and brought up the topic of termination THEN. It may have been a hard discussion, and ultimately one they disagreed on, but it would not have resulted in this.
The issue here is not even so much that the DH has changed his mind, or that they disagree on termination. It is that he thinks that it is ok to want his wife to go through a most horrible trauma (late abortion, which she does not want) so that he is spared potential trauma. It is that he sees the reality of a pretty much fully-formed baby, which is wanted and is thus emotionally already a 'part of' the family as far as the OP is concerned, as disposable and replaceable -'we can have one next year'. That attitude is sickening. I say that as a pro-choice person - this ISN'T about termination in the abstract, not at all, but what appears to be pure, pure selfishness to the point of sociopathy - 'You suffer horribly, the baby suffers fatally, so I don't have any suffering - that's my choice, can you do that please. Then I expect us to be ok afterwards - I expect you to forget all about it, to the extent that we start all over again with another pregnancy and I expect you to be all happy and joyous about it, slate wiped clean.'
It is an utterly bizarre attitude, positively chilling. I cannot understand how any reasonable person could not see, for a start, that even proposing such a course of action would make them a monster in their partner's eyes. Yet this man is crying about 'I think I'm losing you'. And at the same time refusing counselling - he does not see a problem with what he has said and what that says about him.
If I were OP I would want him out of my house not because of a disagreement on termination, but simply because I would be filled with horror at the thought that my husband could think in such an utterly twisted way.
I do not see how the OP could have done anything to change this situation or how talking at an earlier stage could have helped.