More than likely a newly diagnosed patient is an infant or child. My advice for parents is to take a deep breath. This isn't your fault. I can't promise everything will be picture perfect, but, the odds are strongly in your favor. Life expectancy is high and modern medicine is wonderful.
Sometimes BWS newborns need a more interventions at birth. Deep breaths, one day at a time. Remember to also take care of yourself and be good to You. NICU stays are stressful and exhausting, but no matter what I promise you'll get through it.
Pay close attention to doctors, and take notes often. Write down questions to ask, because I promise you that you'll have dozens. Chances are once you see a specific specialist, you will forget what you wished to ask.
Reach out to others with BWS or who have family members who have it. Finding others to connect with is helpful in easing fears. You may also be able to find others in your area and get recommendations on specialists.
The important thing to remember is that on average, you or your loved one will be absolutely fine.