What Causes Newborns to Spit Up Milk?
Apr 14, 2022
Source: Cainiu Health
Dr. Zhang Weiling
Introduction
Spitting up milk in newborns is a normal physiological phenomenon, typically caused by physiological factors, pathological conditions, or improper feeding practices. A newborn’s stomach is not positioned vertically downward but lies horizontally, resulting in a smaller gastric capacity and reduced food storage. Additionally, the lower esophageal sphincter (LES) muscle tone is relatively low in infants, and the cardia (the upper opening of the stomach) is relaxed and does not close tightly; consequently, milk can easily reflux upward, leading to spitting up.
Spitting up milk is a normal physiological phenomenon in newborns, commonly caused by physiological factors, pathological conditions, or improper feeding practices.
① Physiological Causes
A newborn’s stomach is not vertically oriented but lies horizontally. This anatomical arrangement 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 (the upper opening of the stomach) remains relaxed and incompletely closed, making it easier for milk to reflux—resulting in spitting up.
② Pathological Causes
Certain medical conditions—including common colds, bacterial infections, constipation, esophageal atresia, or congenital megacolon—can lead to abnormal or excessive spitting up in newborns.
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. Others may worry that their baby isn’t getting enough milk and thus overfeed them—or use a bottle nipple with an excessively large hole. Furthermore, newborns often move restlessly during feeding or nurse while crying, both of which can also trigger spitting up.
