I remember that ultrasound during the 2nd pregnancy when we found out if we would have a boy or a girl, all the checks for defects, all the blood work, and all that. We were fortunate that our little girl was OK then and was born healthy and strong.
But I also remember the apprehension and then the sadness during the first pregnancy when we found out about 10 weeks in, during a routine ultrasound, that the fetus had no heartbeat. My wife and I sat there in a private room, she cried, I just got lost in my thoughts.
No one ever knows why these things happen, not even the doctors. You can blame God, you can blame genetics, you can blame chance or you can just blame rotten luck. Regardless of what you and your wife decide, remember that *you* will be the rock for your wife. She is carrying this child, she is going to feel like all of this is her fault, or is on her shoulders, or somehow she is the one at fault (common for women). So YOU will be what carries her through this, just as I did for my wife so many years ago. If this is a test, it's a test of your strength and love for her.