Saying 'we're happy with ....' Is very different to saying 'I'm devastated with something my wife is doing.....'
Honestly I can't see how anyone wouldn't feel betrayed by their partner telling someone else their dw or dh is doing something that is devastating them when they haven't been honest to actually have a conversation about it together first.
The op mentions that she knows he wants a bio dd from 1 conversation they had ages ago, he clearly hasn't told the op he is devastated and it doesn't sound like he has even approached the subject recently otherwise why would the op say that they are both happy the appointment has come through. Assuming she's not lying, she clearly thinks that he, like her, is happy that the appointment has come through.
It sounds like they (as a couple) have had high end discussion about this in the past with mutual friends but to me going into too much detail is a betrayal of trust, e.g you might tell a mutual friend your buying a house but I wouldn't expect my dh to go into the ins & outs of the finances of it all. I might tell a friend we're not planning to have more kids (question that often gets asked just after you've had a baby like the op) but I would never, and would be horrified if my dh did, go into the details of the agonising emotional conversations/ arguments etc about it.
People are saying that the dh just needed to confide in a friend, this friend doesn't seem particularly close (ie sibling, old uni friend, best friend, etc) so I would be annoyed at dh disclosing something so personal, after all he's not just talking about his feelings but the family situation.
The be all and end all of this is that he should have behaved like an adult and told you how he felt rather than attention seeking elsewhere!