50mm 1.8 focus issues

Recently I've been taking alot of picture of my baby with the Canon 50mm 1.8 on my Rebel XSI (450D). I take them generally without a flash, in reasonable light (either indoors during the day, or outside in the shade. Some of the pictures turn out great, however it seems like the vast majority of them aren't focused properly. If I shoot at 1.8, the chances of the whole face, or even any of it being in focus are extremely slim. I know that the depth of field is only about an inch, but this should be plenty for a babies face.

Is there something I'm doing wrong? I've tried to go to like 3.6 or so, but then the background is not as blurred as I would like. Is it an issue with the lens, or the camera failing to find the proper focus?