What Causes Newborns to Spit Up Milk?
May 05, 2022
Source: Cainiu Health
Dr. Zhang Weiling
Introduction
Spitting up milk in newborns is a normal physiological phenomenon. Common causes include:
- **Physiological causes**: Newborns have small stomach capacities and can hold only small amounts of milk. Additionally, the lower esophageal sphincter (LES) has relatively low muscle tone and remains relaxed, resulting in incomplete closure—making spitting up more likely.
- **Pathological causes**: Conditions such as colds or bacterial infections may lead to abnormal spitting up in newborns.
Spitting up milk in newborns is a normal physiological phenomenon, commonly caused by physiological factors, pathological conditions, or improper feeding practices.
① Physiological Causes
A newborn’s stomach is not positioned vertically but lies horizontally. This orientation reduces gastric capacity and limits the amount of milk the stomach can hold. Additionally, the lower esophageal sphincter (LES) muscle tone is relatively low in newborns, and the cardia (upper stomach opening) is relaxed and does not close tightly, making it easier for milk to reflux—resulting in spitting up.
② Pathological Causes
Abnormal spitting up may occur in newborns with conditions such as common colds, bacterial infections, constipation, esophageal atresia, or congenital megacolon.
③ Improper Feeding Practices
This is especially common among inexperienced new parents. For instance, some mothers prefer lying down while breastfeeding to conserve energy; however, this face-to-face side-lying position significantly increases the likelihood of spitting up. Parents may also worry that their baby isn’t getting enough milk and thus overfeed them—or use bottle nipples with excessively large holes. Furthermore, newborns often move restlessly during feeding or nurse while crying, both of which can easily trigger spitting up.
