Risk factors

Risk factors for pyloric stenosis include:

• Sex. Pyloric stenosis is seen more often in boys — especially firstborn children — than in girls.
• Race. Pyloric stenosis is more common in whites of northern European ancestry, less common in Black people and rare in Asians.
• Premature birth. Pyloric stenosis is more common in babies born prematurely than in full-term babies.
• Family history. Studies found higher rates of this disorder among certain families. Pyloric stenosis develops in about 20% of male descendants and 10% of female descendants of mothers who had the condition.
• Smoking during pregnancy. This behavior can nearly double the risk of pyloric stenosis.
• Early antibiotic use. Babies given certain antibiotics in the first weeks of life — erythromycin to treat whooping cough, for example — have an increased risk of pyloric stenosis. In addition, babies born to mothers who took certain antibiotics in late pregnancy may have an increased risk of pyloric stenosis.
• Bottle-feeding. Some studies suggest that bottle-feeding rather than breast-feeding can increase the risk of pyloric stenosis. Most of the people who participated in these studies used formula rather than breast milk, so it isn't clear whether the increased risk is related to formula or the mechanism of bottle-feeding.