What is the expected change in a baby's birth weight by the time they reach one year?

By the first year of life, a baby's birth weight typically doubles by around 6 months and then usually triples by the time they reach 12 months. This important growth pattern reflects the rapid development and increasing nutritional needs of infants during their first year.

Doubling the birth weight by 6 months indicates that the baby is receiving adequate nutrition and support for healthy growth. The tripling of the birth weight by 12 months signifies robust physical development, as infants are growing not only in weight but also in length and overall strength.

In contrast to this, the other options do not accurately represent the growth patterns of infants. For instance, suggesting that a baby's weight should double by 3 months is premature, as many babies do not reach this milestone until about 6 months. Claiming the weight would remain the same until 1 year does not align with expected growth trajectories, given the rapid changes that occur during the first year. Likewise, stating that birth weight should triple by 6 months is significantly beyond the normal growth expectations. Thus, the appropriate assessment of a baby's growth reflects that by one year, the expected weight should indeed have doubled by 6 months and tripled by 12 months.