"Many parents fear that babies put to sleep on their backs could choke on spit-up or vomit. According to the AAP, however, there is no increased risk of choking for healthy infants who sleep on their backs. (For infants with chronic gastroesophageal reflux (GER) or certain upper airway malformations, sleeping on the stomach may be the better option. The AAP urges parents to consult with their child's doctor in these cases to determine the best sleeping position for the baby.)"

This is a baby with severe GER issues, so stomach sleeping might be the better option depending on what the pediatrician recommends.