I read a lot about this when DD was little, as my Mum had a coldsore and so we agreed she couldnt come over to visit until it had gone. I read it is particularly dangerous if the Mother doesn't suffer with coldsores (I don't) as the Mum wouldn't have passed on the protection to baby in pregnancy. I would get checked either way but definitely do if you are not a herpes carrier xxx
ETA - it was the first heard about the dangers when Mum said she didn't think she should come over due to a coldsore, as she remembered when my Nan was a maternity nurse she wasn't allowed to go to work with a coldsore. Then I did a lot of research. It was taken a lot more seriously years ago, nobody even mentioned it to me when i was pregnant. NCT and the NHS ought to tell people! xxx