Autism in newborns-3 week old twins?

I just had fraternal twins 3 weeks ago, and although she is only 3 weeks old, my daughter seems to be too good and we are concerned that she may have problems. My son, is showing signs of being able to hear our voices and look in that direction but my daughter seems to constantly be looking out into space. She doesn't look towards sounds or anything. She hardly ever cries, except when she's really hungry she will cry pretty loudly depending how fast I can get her bottle. She doesn't cry when shes being changed or having a bath. She can lay for hours wide awake just looking off into space. I am a huge worry wart but they are so beautiful and I am just concerned. and yes I do have a dr appointment next week, but to the moms out there who know, once you think something is wrong you wont be able to think about anything else. So if anyone has experience in this I would love hearing about it. Thank you.