Hi Gary,
I'm sorry that you've gotten this news. You sound like someone who wants facts, which is the kind of person I was when I was in a similar situation.
Firstly, from advice we got from our consultant, a baby having hydrops this early on in a pregnancy is not good and realistically means that the baby's heart will ultimately stop.
We had bad news at our 13 week scan. At that scan our baby didn't yet have hydrops but did have a cystic hygroma. By the next week however the baby had developed hydrops. We got an amnio and a chromosomal abnormality was confirmed, which wasn't of itself fatal but the existence of the hydrops made it a fatal diagnosis.
Hydrops stops organs developing properly. Ultimately the baby's heart will stop but the baby is perfectly comfortable so don't worry that your baby is in pain. He/she isn't. The baby doesn't know he/she needs these organs yet.
We ultimately waited for our baby's heart to stop, which it did at almost 21 weeks. We were in a different situation to you and terminating would have involved having to travel abroad, very different considerations applied. And when we were told there would be a natural conclusion, with our baby's heart stopping naturally, we decided to let nature take its course. It's an entirely personal decision, you and your partner are only answerable to each other and nobody else needs to know anything.
I then had to have labour induced once our baby's heart stopped. As far as I know this process would have been very similar to labour after a medical termination. It was painful, and as it was my first baby/birth it was 16 hours before our baby was born. Basically, pills for inducing labour were first inserted into my cervix and then other pills were administered orally every 3 hours.
It is a very difficult time. While we were going through it I do remember just wanting the facts laid bare, no candyfloss and making things sound better than they were and then coming home and trying to deal with the facts.
Good luck with your decision. You have a tough time ahead of you. I remember at the start I was like, I'm treating this as a late miscarriage, these things happen all the time etc. But I did change my mind. We did name her, we have a memory box, we got to spend some time with her after birth before saying goodbye etc and that all helped immensely with the grieving process.
Bluebell