Oh sweetheart, i am so so sorry that you have to go through this.
I have been through something almost similar to you, and if it'll help i'm happy to share my story.
I got pregnant with triplets in 2004, and sadly lost one at ten weeks. At my twelve week scan there showed that one of my remaining babies might have a hernia on it's umbilical cord - but obviously at that gestation, it was fat too soon to be sure. I was booked for another scan at 14 weeks, and my consultant wasn't very happy so sent me to another hospital for a more detailed scan the next day.
The scan showed that one of my babies had a condition called Posterior Uretheral Valves, which means that he (it only affects boys)did not have an opening going from his bladder to his urethera so he could not pass urine.
After about 16-18 weeks, unborn babies make their own amniotic fluid, and they do this by drinking in whats there and passing it through their bodies and weeing it out. They also practice breathing with it.
Anyway, the condition that Ciaran had meant that he couldn't wee out, and although his kidneys were making urine, it was simply backing up into his kidneys and he would have had severe renal failure when born, leading to him needing a transplant as soon as was possible.
Also, because he couldn't wee, his lungs were very underdeveloped, and he wouldn't have been able to survive.
Now, here's where my situation differes from yours, Cantdothisagain, in as much as because i was carrying twins i had to think of our other healthy baby, and had to continue with the pregnancy. I did however consider on more then one occasion, putting Ciaran 'to sleep'... it felt like it would be cruel to give birth to him, knowing that to do so would mean he had to die.... but i don't regret any decisions that we made then.
My beautiful, precious boys were born early at 28 weeks, and Ciaran lived for an hour and 42 amazing minutes. He fought so hard to be here, snd to stay with us, and he was so perfect... but it just wasn't his time. I don't regret for one minute having him... not even all the times i'm tormented with the 'what did i do to cause this' questions..
I guess what i'm trying to say, Cantdothisagain, is that firstly... don't rush into any decisions... take time to let this sink it. Secondly... make the best decisions you can with the information you have at the time.
I'm so sad for you that you have to go through this, sweetheart... it really is truly awful.
Please know that we are all here to listen whenever you need to talk xxx