From your baby's first day, doctors will keep track of weight, length, and head
size. Growth is a good indicator of general health. Babies who are growing well are
generally healthy, while poor growth can be a sign of a problem.
How Big Are Newborns?
Newborns come in a range of healthy sizes. Most babies born between 37 and 40 weeks
weigh somewhere between 5 pounds, 8 ounces (2,500 grams) and 8 pounds, 13 ounces (4,000
Newborns who are lighter or heavier than the average baby are usually fine. But
they might get extra attention from the doctors and nurses after delivery to make
sure there are no problems.
Different things can affect a baby's size at birth. The length of the pregnancy
is important. Babies born around their due date or later tend to be larger than those
Other factors include:
Size of parents. Big and tall parents may have larger-than-average
newborns; short and petite parents may have smaller-than-average newborns.
births. If you have twins, triplets, or more, you can
count on your babies being a bit small. Multiples have to share their growing space
in the uterus, and they're 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.
Mom's health during pregnancy. Things that can lead to a lower
birth weight include a mother with high blood pressure or heart problems; or one who
used cigarettes, alcohol, or illegal
drugs during the pregnancy. If the mother has diabetes or is obese, the baby may
have a higher birth weight.
during pregnancy. Good nutrition is vital for a baby's
growth — before and after birth. A poor diet during pregnancy can affect how much
a newborn weighs and how the infant grows. Gaining a lot of weight can make a baby
more likely to be born bigger than average.
Baby's health. Medical problems, including some birth
defects and some infections during the pregnancy, can affect a child's birth weight
and later growth.
What About Preemies?
Premature babies generally
are smaller and weigh less than other newborns. A preemie's weight will largely depend
on how early he or she was born. The time an infant missed being in the womb was growing
time, so the baby has to do that growing after birth.
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 (2,500 grams)
at birth. That's the case for about 1 in every 12 babies in the United States, so
it's quite common.
Very low birth weight means a baby weighs less than 3 pounds, 5 ounces (1,500
Most babies with low birth weight or very low birth weight were born prematurely.
Premature babies get special medical attention right away after they're born. A
specialist called a neonatologist may help care for them. Many
preemies spend time in the neonatal
intensive care unit (NICU) while they get medical care.
Is Bigger Better?
A baby with chubby cheeks and dimpled thighs once 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 very large babies — especially those born to mothers with diabetes, including
— may have problems for a few days keeping blood sugar levels up. They might need
extra feedings or even IV (given into a vein)
to keep those levels from falling too low.
Will My Baby Lose Weight?
Yes, at first. Babies are born with some extra fluid, so it's normal for them to
drop a few ounces when they lose that fluid 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 within the first 2 weeks or so after birth.
During their first month, most newborns gain weight at a rate of about 1 ounce
(30 grams) per day. They generally grow in height about 1 to 1½ 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. If so, talk to your doctor, who may ask you about:
How many feedings a day your baby gets. A breastfed
baby may feed about 8 or more times in a 24-hour period; formula-fed
babies usually eat less often, perhaps every 3 to 4 hours. A lactation (breastfeeding)
counselor can make suggestions to increase comfort and improve
technique, if a mom needs extra help.
How much your baby eats at each feeding. A baby generally nurses
for at least 10 minutes, should be heard to swallow after 3 or 4 sucks, and should
seem satisfied when done. At this age, formula-fed babies may drink up to 3 to 4 ounces
(90 to 120 milliliters) at a time.
How often your baby pees. A breastfed baby may have only 1 or
2 wet diapers a day until the mother's milk comes in. Expect about 6 wet diapers by
3 to 5 days of age for all babies. After that, babies should have at least 6 to 8
wet diapers a day.
How many bowel movements your baby has each day, and what they're like.
Newborns may have only one poopy diaper a day at first. Poop is dark and tarry the
first few days, then becomes soft or loose and greenish-yellow by about 3 to 4 days.
Newborns usually have several poopy diapers a day if breastfed and fewer if formula-fed.
What Else Should I Know?
Being small or large at birth doesn't mean a baby will be small or large later
in childhood or as an adult. Plenty of tall teens began life as small babies, and
the biggest baby in the family 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 how your baby
grows in the years to come.
Whether your baby starts out large, small, or average, in the next few months you
can expect your little one to keep growing fast.