Gastric Emptying in Neonates and Infants After Formula Feeding

Inclusion criteria for study cohort are pediatric patients from Allen Hospital and Morgan Stanley Children's Hospital of New York Presbyterian Hospital who are receiving feeding by formula 1. healthy full-term (postmenstrual age ≥ 36 weeks) newborns aged 0-5 days or 2. healthy infants (4-6 months old and 9-12 months old) Exclusion criteria are individuals who have 1. newborn history of requirement resuscitation at delivery 2. newborn history of admission to the Neonatal Intensive Care Unit 3. any history of hospital admission 4. history of gastroesophageal reflux or other feeding difficulty 5. receiving any medication known to accelerate or delay gastric emptying, including but not limited to opioid-containing medications and antacids.