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.
Other factors include:
-
Size of parents.
Tall parents may have larger-than-average newborns; short parents
may have smaller-than-average newborns.
-
Multiple births.
If you're having twins, triplets, or more, you can count on
your babies being relatively small. Multiples not only have to
share their growing space in the uterus, they also are often born
early, which leads to small size at birth.
-
Birth order.
First babies are sometimes smaller than brothers or sisters born
later.
-
Gender.
Girls tend to be smaller, boys larger, but the differences are
slight at birth.
-
Mother's health during pregnancy.
Factors that can lead to a lower birth weight include a
mother's high blood pressure, heart problems, or use of
cigarettes, alcohol, or illegal drugs during the pregnancy. If
the mother has diabetes, the baby may have a higher birth weight.
All conditions that can affect a baby's weight should be
closely monitored by the mother's doctor. In addition, women
should not smoke, drink alcohol, or use illegal drugs during
pregnancy.
-
Nutrition during pregnancy.
Proper nutrition is essential for a baby's growth in the
uterus and beyond. A poor diet during pregnancy can affect how
much a newborn weighs and how the infant grows.
-
Baby's health.
Medical problems, including some birth defects and certain
infections acquired during the pregnancy, can affect a
child's birth weight and later growth.
Growth and Premature Babies
Premature babies
generally are smaller and lighter than other newborns. A
preemie's weight will be largely determined by how early he or
she was born. The time the infant has missed being in the womb was
growing time, so the baby has to do that growing in the outside
world.
Many pre-term babies are classified as having "low birth
weight" or "very low birth weight." In medical
terms, "low birth weight" means a baby weighs less than 5
pounds, 8 ounces (2,630 grams) at birth. That's the case for
about 1 in every 13 babies in the United States, so it's quite
common. "Very low birth weight" means a baby weighs less
than 3 pounds, 5 ounces (1,587 grams). Most babies with low or very
low birth weight were born prematurely.
Premature babies are given special medical attention immediately
after birth, and a pediatric specialist called a neonatologist may
be involved in their care. Many premature babies spend time in the
neonatal intensive care unit (NICU) while they receive medical
care, including feeding and observation of growth.
Is Bigger Better?
In the old days, a "strapping" baby with chubby cheeks
and dimpled thighs was many people's picture of a healthy
newborn. But a baby born much larger than average may have special
medical problems that need attention. Some exceptionally large
babies, especially those born to mothers with diabetes, including
gestational diabetes, may have problems for a few days keeping
blood sugar levels up and may require extra feedings, or even
intravenous glucose, to prevent those levels from falling too
low.
How Newborns Grow
Babies are born with some extra fluid, so it is perfectly normal
for a newborn to drop a few ounces when that fluid is lost in the
first few days of life. A healthy newborn is expected to lose 7% to
10% of the birth weight but should regain that weight by about 2
weeks after birth.
During their first month, most newborns continue to gain weight
at a rate of at least 5 ounces (141 grams) a week. They generally
grow in height about 1 to 1.5 inches (2.54 to 3.81 centimeters)
during the first month. Many newborns go through a period of rapid
growth when they are 7 to 10 days old and again at 3 and 6
weeks.
Should I Be Concerned?
Newborns are so small, and it can be hard to know if your baby
is gaining weight the way he or she should. You may worry that your
baby has lost too much weight in the first few days or isn't
taking enough breast milk or formula. Most likely, everything is
fine. But if you are concerned at all, check with your doctor.
What's Next?
Being small or large at birth doesn't necessarily mean a
baby will be small or large later in childhood or as an adult.
Plenty of towering teenagers began life as small babies, and the
biggest baby on the block can grow up to be a petite adult.
By the time they're adults, kids tend to resemble their
parents in size. Genetics, as well as good nutrition and your
attention, will play a large part in determining how your baby
grows in the years to come.
Whether your baby starts out large, small, or in between, in the
next few months you can expect your infant to keep growing
fast.
Reviewed by:
Steven Dowshen, MD
Date reviewed: August 2008
Note: All information is for educational purposes only. For specific medical advice,
diagnoses, and treatment, consult your doctor.
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