从Enfamil expert得到的回复, Thank you for contacting the Enfamil® Resource Center. We appreciate your interest in the complimentary multiple birth product sent for your twins. While Enfamil PREMIUM® Newborn Infant Formula is designed for the first 3 months of life, it could be fed to older infants. The 80:20 whey :casein ratio would not be harmful for an older baby, and the formula provides the nutrition necessary for infant formulas for babies from birth to 12 months.