The normal body temperature of a 3-month-old baby should fluctuate between 36.4°C and 37.2°C. Many factors can affect body temperature in small children. For example, crying, breastfeeding, and sweating can all make the body temperature high. If your child has just finished crying, or has just finished eating milk, or has just finished sweating to take his or her temperature, it may be high. It is acceptable if the temperature does not exceed 38℃, but 37.5℃. If the temperature exceeds 38℃ or higher, it is definitely abnormal and there should be a fever. A child’s temperature should be taken in a quiet state, without eating or sweating is more accurate. Generally the most common cause of fever in 3-month-old children is cold and cold. The more common means of transmission is mainly cross-infection that occurs when an adult in the family has a cold or a relatively large child has a cold. The family has a relatively large adult cold, or a large child cold, must pay attention to wear a mask, pay attention to respiratory isolation, do not kiss, feed the child, kiss, feed the child, it is easy to infect the child lead to pneumonia, 3 months of the child resistance is still very low.