You talk about the husband wanting to abide by the wife's wishes - I'll credit he believes that to be true, but I don't personally believe that any woman who is pregnant and intent on giving birth would freely give a direction that should she die her unborn child should be taken with her. I've seen what women do to protect the lives of their children, some giving their own life to save their child. I think it's an insult to the memory of this woman that her husband believes she wouldn't want everything done to save her child.
And you're right - the husband and wife were both paramedics. As such, nothing would convince me that they wouldn't know the absolute need of having their wishes in writing in order for them to be valid. Perhaps it's just a matter of the invincibility of youth that nothing formal was put in writing, but there wasn't.
As for leaving the decision to next of kin, I would tend to agree - where we disagree here is what is in the best interest of the developing life. It's not unheard of that government would step in to protect the interests of the vulnerable when the guardians of those interests are acting in their own interests rather than that of the patient.