Low birthweight is a weight of less than 5 pounds, 8 ounces (2,500 grams) at
birth. Very low birthweight is a weight of less than 3 pounds, 5 ounces (1,500
grams).
There are two categories:
- Preterm births
(also called premature births) occur before the end of the 37th week
of pregnancy. More than 60 percent of low-birthweight babies are
preterm. The earlier a baby is born, the less developed its organs
will be, the less it is likely to weigh, and the greater its risk
for many problems. (Some premature babies born near term, at around
35 to 37 weeks, do not have low birthweight, and may have only mild
or no health problems as newborns.)
- Small-for-date
babies ("small
for gestational age" or "growth-restricted")
may be full-term but are underweight. Their low birthweight results,
at least partly, from slowing or temporary halting of growth in the womb.
Some babies are both premature and growth-restricted. They are at high risk
for many problems linked to low birthweight. [BACK
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What
causes low birthweight?
We
know only some of the reasons babies are born too small, too soon,
or both. Fetal defects that result from genetic conditions or environmental
factors may limit normal development. Multiples (twins, triplets,
or higher) often are low birthweight, even at term. If the placenta
is not functioning properly, a fetus may not grow as well as it should.
A mother's medical
problems influence birthweight, especially if she has high blood pressure,
certain infections or heart, kidney or lung problems. An abnormal uterus
or cervix can increase the mother's risk of having a premature, low-birthweight
baby. However, the causes of preterm labor—which often results
in a low-birthweight baby—are poorly understood.
A mother's actions
before and during pregnancy may affect birthweight. All women planning
pregnancy should:
- Have a pre-pregnancy
checkup.
- Consume a multivitamin
containing 400 micrograms of the B vitamin folic acid (the amount
found in most multivitamins) every day before and in the early
months of pregnancy.
- Stop smoking.
Smokers have smaller babies than non-smokers, on average, and maternal
exposure to another person’s smoking also may
decrease the baby’s birthweight.
- Stop drinking
alcohol and/or using illicit drugs, or prescription or over-the-counter
drugs (including herbal preparations) not prescribed by a doctor
aware of the pregnancy. Drug and alcohol use limits fetal growth
and can cause birth defects.
Once pregnant:
- Get early,
regular prenatal care.
- Eat a balanced
diet with enough calories (usually about 300 calories a day more
than a woman normally eats). Since a fetus is nourished by what
a mother eats, it can suffer if the mother eats poorly.
- Gain enough
weight. Health care providers recommend that a woman of normal
weight gain 25 to 35 pounds during pregnancy.
Socioeconomic factors
such as low income and lack of education also are associated
with increased risk of having a low-birthweight baby, although the
underlying reasons for this are not well understood. Women under
17 or over 35, unmarried mothers and women who have had a previous
preterm birth, are at increased risk of having low-birthweight babies.
Teenagers, in particular, may not have good health habits. Women
who experience excessive stress and victims of domestic violence
or other abuse also may be at increased risk of having a low-birthweight
baby. [BACK TO TOP]
Can low birthweight
be prevented?
A recent study showed that it is difficult to predict which women
are going to deliver preterm. When a woman develops preterm labor,
a doctor may recommend a medication (called a tocolytic) in an attempt
to prevent preterm delivery. These drugs often postpone delivery
for only a day or two, but even such a short delay can be helpful,
as explained below.
Doctors continue
to seek better ways to prevent and treat preterm labor. However, there
are some things a pregnant woman or woman planning pregnancy can do
to reduce her risk of having a low-birthweight baby. The most effective
way to prevent low birthweight is to see a doctor before pregnancy
and, once pregnant, get early and regular prenatal care. A pre-pregnancy
visit is especially crucial for women with chronic disorders such as
diabetes and high blood pressure. Good control of these disorders,
starting before pregnancy, reduces the risk of pregnancy complications.
All women can benefit from early advice on good nutrition, as well
as about the importance of stopping risky behaviors, especially smoking,
drinking alcohol and taking unprescribed drugs.
A 1996 study published
in the American Journal of Clinical Nutrition suggested that consuming
the recommended prenatal amount of folic acid throughout pregnancy
may reduce the risk of having a preterm and low-birthweight baby.
When women receive
adequate prenatal care, many problems can be identified early,
allowing treatment that may reduce their risk of having a low-birthweight
baby. [BACK TO TOP]
How
is fetal growth restriction treated?
About 5 percent of fetuses are considered growth restricted. A
doctor may suspect fetal growth restriction if the mother’s
uterus is not growing at a normal rate. This can be confirmed with
a series of ultrasound examinations that monitor how quickly the
fetus is growing. In some cases, fetal growth can be improved by
treating any condition in the mother that may be contributing.
For example, a woman with a pregnancy-related form of high blood
pressure called preeclampsia would generally be treated with bedrest
and, sometimes, blood pressure medications. A woman who smokes
would be counseled to stop.
The doctor will
closely monitor the well-being of a growth-restricted fetus, using
ultrasound and fetal heart rate monitoring. If these tests show that
the baby is in trouble, due to lack of oxygen or other problems,
early delivery may be recommended. [BACK
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What problems occur
in low-birthweight babies?
Low-birthweight babies are more likely than babies of normal weight
to have health problems during the newborn period. Many of these
babies require specialized care in intensive care nurseries to help
them survive. Serious medical problems are most common in babies
born at very low birthweight.
A low-birthweight,
premature baby is at greater risk of developing breathing problems.
According to the American Lung Association, about 25,000 babies
a year, most of whom were born before the 34th week of pregnancy,
suffer from respiratory distress syndrome (RDS). Babies with RDS
lack a substance called surfactant that keeps small air sacs in the
lungs from collapsing. Treatment with surfactant helps babies breathe
more easily and, since it was widely introduced in 1990, infant deaths
due to RDS have been reduced by two-thirds.
Babies with RDS may
need additional oxygen and mechanical breathing assistance to keep
their lungs expanded. The air may be delivered through small tubes
in the baby’s nose, or through a tube that has been inserted
into his windpipe. The tube helps the baby breathe, but does not breathe
for him. The sickest babies may temporarily need the help of a respirator
to breathe for them while their lungs mature. They also may be treated
with a gas called nitric oxide, which can make breathing more effective
by helping blood vessels in the lungs to relax.
Bleeding in the brain
(called periventricular and/or intraventricular hemorrhage) occurs
in 10 to 50 percent of very-low-birthweight infants, usually in the
first four days of life. The bleeds are generally diagnosed with an
ultrasound examination. Most are mild and resolve themselves with no
or few lasting problems. More severe bleeds can cause the fluid-filled
spaces (ventricles) in the brain to expand rapidly, creating pressure
on the brain that can lead to brain damage. In such cases, surgeons
may insert a tube into the brain to drain the fluid and reduce the
risk of brain damage. In milder cases, drugs may reduce fluid buildup.
Premature babies
may have a dangerous heart problem called patent ductus arteriosus
(PDA). Before birth, a large artery called the ductus arteriosus lets
the blood bypass the baby’s nonfunctioning lungs. In premature
babies, the artery may not close properly, and even lead to heart failure.
Babies with PDA are treated with a drug that helps close the ductus,
though surgery may be necessary if the drug doesn’t work.
Some premature babies
have a dangerous intestinal problem called necrotizing enterocolitis
(NEC), which leads to feeding difficulties, abdominal swelling and
other complications. Babies with NEC are treated with intravenous fluids
and antibiotics while the bowel heals. In some cases, surgery is necessary
to remove damaged sections of intestine.
Retinopathy of prematurity
(ROP), caused by an abnormal growth of blood vessels in the eye that
can lead to vision loss, occurs mainly in babies born before 32 weeks.
Most cases heal by themselves with little or no vision loss. More severe
cases are treated with a laser or with cryotherapy (freezing) to preserve
vision.
Many premature,
low-birthweight babies lack enough body fat to maintain a normal
body temperature. Low body temperature can slow growth and contribute
to breathing problems and other complications. These babies are placed
in an incubator or warmer right after birth to help them maintain
a normal body temperature. [BACK
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Can medical problems
in low-birthweight premature newborns be prevented?
When a doctor suspects that a woman may deliver preterm, he may suggest
treating her with drugs called corticosteroids. These drugs cross
the placenta and speed maturation of the fetal lungs, reducing infant
deaths by 30 percent and cutting the incidence of the two most serious
complications of premature birth, RDS (by 50 percent) and bleeding
in the brain (by 70 percent). These drugs are given by injection,
and are most effective when administered at least 24 hours before
delivery. This delay is a main reason for use of tocolytic drugs;
the delay also allows for the mother to be transported to a medical
center that is equipped to handle high-risk deliveries and care of
sick and premature newborns. [BACK
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Preterm Labor
Preterm labor is labor that occurs before your 37th week of pregnancy. (Most
pregnancies last 38-42 weeks; your due date is 40 weeks after the first
day of your last menstrual period.) Preterm labor can happen to any woman:
Only about half the women who have preterm labor fall into any known risk
group. About 12 percent of births (1 in 8) in the United States are preterm.
Babies who are born preterm are at higher risk of needing hospitalization,
having long-term health problems and of dying than babies born at the right
time.
Preterm labor may
sometimes be stopped with a combination of medication and rest. More
often, birth can be delayed just long enough to transport the woman
to a hospital with a neonatal intensive care unit (NICU) and to give
her a drug to help speed up her baby’s lung development.
What you can do:
Call your health care provider or go to the hospital right away if
you think you are having preterm labor. The signs of preterm labor
include:
- Contractions
(your abdomen tightens like a fist) every 10 minutes or more often
- Change in vaginal
discharge (leaking fluid or bleeding from your vagina)
- Pelvic
pressure—the feeling that your baby is pushing down
- Low,
dull backache
- Cramps that
feel like your period
- Abdominal cramps
with or without diarrhea
Your provider may
tell you to:
- Come into the
office or go to the hospital
- Stop what you're
doing. Rest on your left side for one hour
- Drink 2-3 glasses
of water or juice (not coffee or soda)
If the symptoms get
worse or do not go away after one hour, call your health care provider
again or go to the hospital. If the symptoms go away, relax for the
rest of the day. If the symptoms stop but come back, call your health
care provider again or go to the hospital.
You don’t need
to have all the symptoms to have preterm labor. Take action even if
you have only one.
Learn more about
the March of Dimes campaign to reduce preterm birth. [BACK
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Gestational Diabetes
People with diabetes do not produce enough insulin, or their insulin
does not work well. Insulin is a hormone that is produced by
the pancreas. It lets the body turn blood sugar into fat or energy.
Gestational diabetes is diabetes that develops during pregnancy.
About 3 to 5 percent of pregnant women develop gestational diabetes.
If gestational diabetes
is left untreated, the fetus will receive too much blood sugar and
will grow too large. After birth, the baby may have breathing difficulties,
low blood sugar and jaundice.
Gestational diabetes
generally goes away after delivery, but women who get it face about
a 50 percent chance of having it again in another pregnancy, and a
50 percent risk of developing diabetes later in life.
What you can do:
You will probably be screened for gestational diabetes between
your 24th and 28th week of pregnancy. If you do have gestational
diabetes, you can probably control it with diet and exercise.
If these fail, you may have to give yourself insulin injections
and monitor your blood sugar levels at home. A weight loss
and exercise program started after delivery can help reduce
the risk of developing diabetes in subsequent pregnancies as
well as later in life. [BACK
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Pregnancy-Induced
Diabetes
About 3 to 5 percent of pregnant women develop diabetes for the
first time during pregnancy. This type of diabetes, called gestational
diabetes, occurs when pregnancy hormones interfere with the body’s ability to use insulin—the
hormone that turns blood sugar into energy—resulting in high blood
sugar levels. You are at increased risk if you are over age 30, obese,
have a family or personal history of diabetes, or previously gave birth
to a baby who weighed more than 9 pounds or was stillborn.
If a woman with gestational
diabetes isn’t treated, her fetus will receive too much blood
sugar and may grow very large. Oversized babies are at risk of birth
injuries during vaginal delivery, so they often must be delivered by
c-section. Babies of mothers with gestational diabetes also can have
breathing difficulties, low blood sugar and jaundice during the newborn
period.
Most women with gestational
diabetes have no symptoms, though a few may experience extreme hunger,
thirst or fatigue. Your health care provider will probably screen you
for gestational diabetes between your 24th and 28th week of pregnancy.
At the screening, you’ll drink a sugary liquid and then take
a blood test one hour later. If your blood sugar level is high, you’ll
need to take a similar test over three hours to determine whether you
have gestational diabetes.
If you do have gestational
diabetes, you’ll be able to control it with diet and exercise.
Your health care provider or a dietitian will recommend an individualized
diet that takes into account your weight, stage of pregnancy and food
preferences. Most likely, 10 to 20 percent of your calories should
come from protein (meat, poultry, fish), about 30 percent from fats,
and the remainder from carbohydrates (pasta, rice, fruits, and vegetables).
Sweets might be limited.
At least once a week,
you’ll visit your health care provider to get your blood sugar
levels checked. If your diet fails to stabilize your blood sugar levels
after about two weeks, you’ll probably have to give yourself
daily insulin shots throughout your pregnancy and monitor your blood
sugar levels at home.
While gestational
diabetes generally goes away after delivery, women who get
it face about a 50 percent risk of developing diabetes later in life
and also have a 50 percent chance of gestational diabetes in another
pregnancy. Starting a weight loss and exercise program after delivery
can help reduce your risk. [BACK
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Anemia
Anemia is a common condition in pregnancy. It means that the number and/or
size of the person’s red blood cells are below normal. Red blood
cells carry oxygen around your body and to your baby.
The usual cause of
anemia in pregnancy is iron deficiency. Iron helps create red blood
cells. The recommended amount of iron you need each day doubles during
pregnancy from about 15 milligrams (mg) per day to 30 mg per day. Most
pregnant women get this amount from a combination of eating foods that
contain iron and taking a prenatal vitamin. Some women need additional
iron supplements to keep their levels of hemoglobin (a protein in red
blood cells that contains iron and carries oxygen) in a normal range.
Anemia, unless it
is severe, is unlikely to harm your baby, although iron deficiency
has been linked to an increased risk of preterm birth and low birthweight.
Anemia can also make you feel more tired than usual during your pregnancy.
What you can do:
You will probably be tested for anemia at least twice during your pregnancy—at
your first prenatal visit and then again between 24 and 28 weeks. If you are
anemic your health care provider may prescribe an iron supplement. You can
help reduce your risk of anemia by eating foods that contain iron all throughout
your pregnancy.
These include:
- Red meats
- Shellfish
- Poultry
(dark meat)
- Fortified breakfast
cereals (check the box to see if the cereal contains iron)
- Oatmeal
- Blackstrap
molasses
- Spinach and
other leafy green vegetables
- Baked potato,
with skin
- Cooked beans
- Raisins, dates,
prunes, figs, apricots
Foods containing
vitamin C can increase the amount of iron your body absorbs from
the foods listed above and from your prenatal vitamin or iron supplement.
So it’s a good idea to eat foods such as orange juice, tomatoes, strawberries
and grapefruit. Avoid coffee and tea with meals, as they may decrease iron
absorption.
Some iron supplements
may cause constipation or nausea. You may have to try different brands
to see which works best for you. You can also fight constipation by
increasing the amount of water you drink and by eating more fiber,
which is found in whole grain foods, breakfast cereals, fruits and
vegetables.
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