"Regurgitation (spitting up) is the passive movement of stomach contents into the pharynx or mouth" (Baird et al., 2015).

Regurgitation is the most common functional gastrointestinal disorder in infants younger than 12 months (Zeevenhooven et al., 2017). Regurgitation in infants is the most frequent symptom of gastroesophageal reflux and resolves usually around 12 months of age without treatment, it is benign as long as no "troublesome" symptoms occur (Baird et al., 2015, Leung & Hon, 2019).