What is the ideal body weight of a 16-week-old infant whose birth weight was 3¾ kg?

To determine the ideal body weight of a 16-week-old infant, one effective guideline is that by four months of age, a well-fed infant generally doubles their birth weight. In this case, the infant's birth weight was 3¾ kg, which is 3.75 kg. When this weight is doubled, the predicted ideal weight would be 7.5 kg (3.75 kg x 2).

Looking at the options provided, the closest answer to this ideal weight is 8 kg, which aligns well with the general growth expectations for infants over that time frame. Infants typically gain weight at a rapid pace in the early months, so it is reasonable to estimate that a healthy 16-week-old could reach or approximate this figure, thus making 8 kg an appropriate choice.

In this context, the other options reflect weights that are below the expected doubling of the birth weight, indicating less than ideal growth or weight gain for the infant’s age. Hence, they do not meet the typical growth expectations for that developmental stage.