Hi
37 is still young in the grand scheme of things. I think it is a waiting game- see what the post mortem comes up with.
I had my 1st at 39 with one previous miscarriage, I got pregnant again at 39, but unfortunately it wasn't to be. A scan at 13 weeks showed cystic hygroma and generalised edema, I was told if I opted not to terminate I would miscarry anyway.
I don't know, I'm no expert, but perhaps nothing was picked up at your 12 week scan, but your baby may have been poorly anyhow.
I don't think these things are rare, I know people who have given birth to stillborn babies, I know others who have found out awful news at 20 week scan.
I still never thought this would happen to me, but it did!
The consultant said to me, I hope this does not put you off trying for another. She clearly did not see this as an issue and she was an expert in high risk pregnancies.
We are waiting for genetic counselling and then we will go from there.
I know how you feel though, I too am lucky to have a beautiful baby, but was so excited to have a brother or sister for him. I don't think you can prepare yourself for not having another baby. Give your body a bit of time to heal and get the results from your post mortem, one step at a time. At 37 there's most likely some good eggs left in there, and if there isn't...well you will just have to deal with that if and when the time comes.