uneven pupil dilation

Last night I noticed My 3 month old's left eye is more dialated than her right. This is the first I've noticed it and I stare at her all day usually. She's acting okay, smiling as usual the past few days it seemed like she might be babbling less but I thought it was just her learning more playing n being tired.  But she's babbling a lot now and still very alert. Anyone familiar with this? Kinda freaking out here.. Headed to doctor this afternoon anyway