Obama turned right on cue.
Drudge has this up.
The chubby friend’s facial expressions really do look like she’s in communication with someone else, responding to cues, and cueing the pregnant woman. And the woman to her right does whisper something that sets it all going. There is no obvious trigger for Obama to turn around, no indication that the pregnant woman said anything, and she does not faint until Obama turns around and looks at her.