Dr. Erin Hager of the University of Maryland School of Medicine and colleagues had low-income moms of overweight toddlers choose silhouettes that the moms thought represented the size of their child.
"Ninety-four percent of the mothers of overweight toddlers chose a silhouette that was two or more images smaller than their child's true body size," Hager said in a statement. "The mothers of normal-weight toddlers also estimated wrong."
This doesn't mean toddlers should go on diets, but Hager said mothers do need to watch what their children eat, and pay attention to whether they're active enough -- and whether they're big, or right-sized.
The study was published in the Archives of Pediatrics and Adolescent Medicine.