In their first year, newborns grow a big way, with most tripling their birth weight and increasing their length by about 50%.
From your baby's first day,
health care providers will keep track of weight, length, and head size.
Growth is a good indicator of general health, and babies who are
progressing well are generally healthy, while poor growth can be a sign
of a problem.
What Newborns Weigh
Just like adults, newborns come in a range of healthy sizes. Most
full-term babies (born between 37 and 40 weeks) weigh somewhere between
6 pounds, 2 ounces (2,812 grams) and 9 pounds, 2 ounces (4,173 grams).
Their average length ranges from 19 to 21 inches (48 to 53 centimeters).
A newborn who is lighter or heavier than the average range
is probably perfectly fine but might receive extra attention from the
doctors and nurses after delivery just to make sure there are no
problems.
A number of things can affect a baby's size at birth. The length of
the pregnancy is important. Babies born at their due date or later tend
to be larger than those born earlier. Babies born prematurely are often
smaller than full-term babies.