. >> reporter: in addition to blocks and snack time, this is little rhys devine's daily routine. >> rhysy ceri and rory's california home is littered with toys and medical equipment. the effects of having a baby with s.m.a. the rare genetic disease slowly killing the motor neurons in their daughter's spinal cord. >> you're such a brave girl. you didn't even cry when they put the iv in. >> reporter: they're now waiting to find out if the most expensive drug in the world, worth $2 million, will help save her life. >> it's a couple days after infusion, and rhys is just having a crummy day. and it just sucks. and i just feel bad that i can't help her. >> reporter: were you nervous that it might not work? >> i don't know if we were nervous that it wouldn't work. i never kind of let myself think that. >> reporter: as the couple waited to find out if zolgensma worked for rhys, ceri continued to document the highs and lows on social media. >> look at you go, rhys. >> reporter: she also relied on a facebook group for s.m.a. parents. >> my name is erin, and i'm a mother to emma. she is a 4-year-old