Wow, I'm so very sorry to read this. Such a loss with the first baby and now your second one as well. If it were me, I would 100 percent go or a second opinion. I've read about this syndrome. Many who have it do not show signs of it immediately and do so in later childhood and adulthood. But it can be quite debilitating. Having the heart involved is not actually the most common feature making this rare but motor function is often greatly impacted. It's a difficult disorder. I did read that there is not a strong inheritance link that they can trace. That you've had two children with the issue makes you wonder but there is a possibility this is chance. Hard to believe but running in families has not been proven that I've read and it is more a random occurrence. People who do live with this disorder do physical or physio therapy, occupational therapy, take medication if they have seizures and palliative care.
I would absolutely get a second opinion and maybe talk to a genetic specialist as well or developmental pediatrician for input.
I wish you much luck on this journey. It has to be so difficult!
So sorry for the news you have gotten, this must be very difficult to process. It sounds like your wife has only had an ultrasound, has she thought about doing further testing- like a fetal MRI? I would hesitate (personally) to make such a big decision without further testing, second opinions, and meeting with a pediatric neurologist to discuss the findings of the first ultrasound, as well as possibly a follow up one and other tests like a fetal MRI. Get more information from more medical professionals- this is a very hard process with such a big worry, but the research will really help you as you work through this process- let us know how you and your wife, and baby are doing...