What Causes Newborns to Spit Up Milk?
May 25, 2022
Source: Cainiu Health
Dr. Zhang Weiling
Introduction
Spitting up milk in newborns is a normal physiological phenomenon. Common causes include:
- Newborns have small stomach capacities, limiting the amount of milk they can hold.
- The lower esophageal sphincter (LES) in infants has relatively low muscular tone and remains relaxed, resulting in poor closure and increased susceptibility to spitting up.
- Illnesses such as colds or bacterial infections may lead to abnormal spitting up.
- Improper feeding techniques can also easily trigger spitting up.
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 vertically oriented but lies horizontally. This anatomical configuration reduces gastric capacity and limits the volume of milk it 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. Parents may also worry that their baby isn’t getting enough milk and thus overfeed them—or use bottle nipples with overly large holes. Furthermore, newborns often move restlessly during feeding or nurse while crying, both of which can contribute to spitting up.
