By the end of six months, an infant's birth weight should ideally be:

By the end of six months, it is expected that an infant's birth weight will have doubled. This milestone reflects normal growth and development during this critical period of an infant's life.

Infants typically double their birth weight by around five to six months of age due to their rapid growth and increased nutritional needs. This doubling is an important indicator of adequate feeding and health. It shows that the infant is receiving sufficient nutrients necessary for growth, which includes both physical weight and overall development.

Understanding this growth pattern is crucial for parents and caregivers, as it helps in monitoring the health and nutritional status of the infant. Observing whether an infant has reached this milestone can inform healthcare providers about the effectiveness of feeding practices and whether any intervention might be necessary.

Other options do not align with the typical growth patterns seen in infants within this age range. For instance, a weight increase of only 25% or a maintenance of the same weight would indicate potential concerns regarding nutrition and health. Meanwhile, the expectation that an infant could triple their birth weight usually occurs by the end of the first year, not at six months.