The treatment of pulmonary stenosis in 42-day-old infants mainly depends on the severity of the child’s condition, and conservative treatment and surgical treatment can be taken in conjunction with the child’s specific situation. 1. Conservative treatment: If the pulmonary stenosis is only mild, the child does not have obvious clinical symptoms, and it will not affect daily life, work and study, it can be left untreated for the time being, and the child can come to the hospital for regular checkups. 2. Surgery: If the condition of pulmonary artery stenosis is more serious, and the baby has difficulty in breathing and limitation of activities, the baby may need to cooperate with the doctor to receive surgical treatment. Commonly used surgical treatments include percutaneous balloon pulmonary valvuloplasty, direct cardiac surgery, transthoracic pulmonary valve balloon dilatation, etc. It is recommended to take your infant to the hospital as soon as possible for a thorough examination. It is recommended to take the infant to the hospital for a comprehensive physical examination as soon as possible, and formulate a reasonable treatment plan under the guidance of professional doctors.