ignore the fact that it's in the DM, which does love scary health stories - it is a very very rare problem and the parents involved were very unlucky, but it did happen to them, and they are very keen that it doesn't happen to anyone else.
I would seek advice from GP/midwife on what precautions to take in the weeks ahead - maybe you can be tested for antibodies, as you may have them, even if you dont' remember ever having a coldsore in the past? in which case you could probably stop worrying, as your baby should be protected too (I'm not a doctor so don't take my word for it!).
I would guess it is more of an issue if the baby doesn't have antibodies and comes into contact with somebody with a cold sore in its first few days and weeks, and not such an issue for you as a pregnant woman with 8-12 weeks to go, but definitely definitely get someone medical to give you advice, just in case it is a danger.
p.s. if you've been together that long and it's not DP's first coldsore, I would guess you probably do have the antibodies, even if you don't get coldsores yourself - but I would still get it checked out!