Lexi has been sleeping through the night lately but of course on the night I went out with my sisters & got to bed late she woke up almost every 3 hours!! The other night I went to dinner & a late movie with my sisters. I got to bed at about 11:45. Steve said Lexi woke up at 9:15. Then she woke up at 12:30, 2:30, & 5:30! Then last night she completely slept through the night again! Why do babies do that?! How do they know when we're gone? I put her to bed before I went out so as far as she knew the night started normally.