Figure 3. Observed and fitted yawning and non-yawn mouth opening frequencies by gestational age.

Left panel: Mean observed number of yawn (red solid square) and non-yawn (blue unfilled triangle) mouth openings for each gestational age over 600 seconds of observation. Right panel: Fitted 600-second counts from Poisson mixed effects model for an average fetus for yawning (red solid line) and non-yawn (blue dashed line) mouth openings.