เฉลี่ยประมาณ 3-3.5 ค่ะ ข้อมูลเพิ่มเติม https://th.theasianparent.com/%E0%B8%99%E0%B9%89%E0%B8%B3%E0%B8%AB%E0%B8%99%E0%B8%B1%E0%B8%81%E0%B8%95%E0%B8%B2%E0%B8%A1%E0%B9%80%E0%B8%81%E0%B8%93%E0%B8%91%E0%B9%8C%E0%B8%82%E0%B8%AD%E0%B8%87%E0%B8%97%E0%B8%B2%E0%B8%A3%E0%B8%81/