What are three risk factors for infantile hypertrophic pyloric stenosis?

Infantile hypertrophic pyloric stenosis is a condition characterized by the narrowing of the pylorus, which obstructs the passage of food from the stomach to the small intestine. Certain risk factors are commonly associated with this condition, making option B the correct choice.

The identification of a first-born male is supported by research, which indicates that this condition is more prevalent in males, particularly those who are first-born. Additionally, maternal ingestion of erythromycin during pregnancy has been linked to an increased risk of pyloric stenosis in infants. This association can be attributed to the effects of the medication on gastrointestinal motility and development during critical periods of fetal growth. Formula feeding is also commonly associated with this condition, as studies suggest that infants who are formula-fed may have a higher incidence of pyloric stenosis compared to those who are breastfed.

In considering the other options, they present combinations of risk factors that do not align with the established epidemiological findings related to infantile hypertrophic pyloric stenosis. Elements such as maternal smoking or breastfeeding do not show a conclusive link to increased risk, especially in the context of the question. Thus, option B effectively encompasses the recognized risk factors tied to the development of this condition in infants.