Reflux in babies is primarily caused by an immature lower esophageal sphincter (LES), the muscle that acts as a valve between the esophagus and stomach. In infants, this muscle is not fully developed, so it may open too easily or not close properly, allowing stomach contents, including milk and acid, to flow back up into the esophagus. This leads to spitting up or vomiting, which is common and usually harmless in babies
. Additional factors contributing to reflux in babies include:
- The baby's esophagus being shorter or narrower than normal, making it easier for stomach contents to reflux and irritate the esophagus lining
- Feeding practices such as overfeeding or feeding too quickly, which can stretch the stomach and increase pressure on the LES, causing it to open and reflux to occur
- The baby's position during and after feeding; lying flat can promote reflux, while keeping the baby upright can help reduce it
- Other less common causes include conditions like gastroesophageal reflux disease (GERD), pyloric stenosis, food intolerances (e.g., cow's milk protein), or anatomical issues like hiatal hernia
Most babies outgrow reflux as their LES matures and their digestive system develops, typically within the first year
. Reflux becomes a concern if it causes pain, poor feeding, or other complications, which may indicate GERD or other underlying conditions
. In summary, reflux in babies is mainly caused by the immaturity of the LES muscle allowing stomach contents to flow back into the esophagus, combined with factors like feeding volume, position, and sometimes anatomical or medical conditions
