Weight And Length

Full-term babies are born weighing between 6 and 8 1/2 pounds; some weigh more and some weigh less. In most cases, it's a matter of genetics: Small parents tend to have small babies, while large parents typically have larger offspring. In a few cases, the birth weight of the baby is affected by medical problems in the mother or the baby. For example, mothers who develop diabetes (high blood sugar) during pregnancy tend to give birth to larger babies.

No matter what your child's birth weight, it's typical and perfectly normal for newborns to lose as much as 10 percent of their body weight in the first few days because of lost fluids. This lost water weight is usually regained within the first two weeks, as your newborn starts feeding regularly.

Most babies gain about 1 ounce per day during the first month, and at a slightly slower rate thereafter. By the end of the first month, your baby will probably weigh 2 pounds more than at birth. Most babies should double their birth weight by 4 to 6 months of age and triple it by their 1st birthday.

Lengthwise, the typical baby is between 18 and 22 inches at birth, but some are shorter and some are longer. Like weight, length (and later, height) is usually determined by the height of the baby's parents.

Your baby will probably increase his or her length by approximately 10 inches in their first year of life. Length increases more slowly than weight. Most babies do not double their birth length until 4 years of age.

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