Diabetes (actual name is diabetes mellitus) of any kind is a disorder that prevents the body from using food properly. Normally, the body gets its major source of energy from glucose, a simple sugar that comes from foods high in simple carbohydrates (e.g., table sugar or other sweeteners such as honey, molasses, jams, and jellies, soft drinks, and cookies), or from the breakdown of complex carbohydrates such as starches (e.g., bread, potatoes, and pasta). After sugars and starches are digested in the stomach, they enter the blood stream in the form of glucose*. The glucose in the blood stream becomes a potential source of energy for the entire body, similar to the way in which gasoline in a service station pump is a potential source of energy for your car. But, just as someone must pump the gas into the car, the body requires some assistance to get glucose from the blood stream to the muscles and other tissues of the body. In the body, that assistance comes from a hormone called insulin. Insulin is manufactured by the pancreas, a gland that lies behind the stomach. Without insulin, glucose cannot get into the cells of the body where it is used as fuel. Instead, glucose accumulates in the blood to high levels and is excreted or ?spilled? into the urine through the kidneys.
When the pancreas of a child or young adult produces little or no insulin we call this condition juvenile?onset diabetes or Type I diabetes (insulin?dependent). This is not the type of diabetes you have. Unlike women with Type I diabetes, women with gestational diabetes have plenty of insulin. In fact, they usually have more insulin in their blood than women who are not pregnant. However, the effect of their insulin is partially blocked by a variety of other hormones made in the placenta, a condition often called insulin resistance.The placenta
performs the task of supplying the growing fetus
with nutrients and water from the mother's
circulation. It also produces a variety of hormones
vital to the preservation of the pregnancy.
Ironically, several of these hormones such as
estrogen, cortisol, and human placental lactogen
(HPL) have a blocking effect on insulin, a
?contra?insulin? effect. This contra?insulin effect
usually begins about midway (20 to 24 weeks) through
pregnancy. The larger the placenta grows, the more
these hormones are produced, and the greater the
insulin resistance becomes. In most women the
pancreas is able to make additional insulin to
overcome the insulin resistance. When the pancreas
makes all the insulin it can and there still isn't
enough to overcome the effect of the placenta's
hormones, gestational diabetes results. If we could
somehow remove all the placenta's hormones from the
mother's blood, the condition would be remedied.
This, in fact, usually happens following delivery.
How does gestational diabetes differ from other
types of diabetes?
There are several
different types of diabetes. Gestational diabetes
begins during pregnancy and disappears following
delivery. Another type is referred to as
juvenile?onset diabetes (in children) or Type I (in
young adults). These individuals usually develop
their disease before age 20. People with Type I
diabetes must take insulin by injection every day.
Approximately 10 percent of all people with diabetes
have Type I (also called insulin?dependent
diabetes).
Type II diabetes or noninsulin?dependent diabetes
(formerly called adult?onset diabetes) is also
characterized by high blood sugar levels, but these
patients are often obese and usually lack the
classic symptoms (fatigue, thirst, frequent
urination, and sudden weight loss) associated with
Type I diabetes. Many of these individuals can
control their blood sugar levels by following a
careful diet and exercise program, by losing excess
weight, or by taking oral medication. Some, but not
all, need insulin. People with Type II diabetes
account for roughly 90 percent of all diabetics.
Who is at risk for developing gestational
diabetes and how is it detected?
Any woman might
develop gestational diabetes during pregnancy. Some
of the factors associated with women who have an
increased risk are obesity; a family history of
diabetes; having given birth previously to a very
large infant, a stillbirth, or a child with a birth
defect; or having too much amniotic fluid
(polyhydramnios). Also, women who are older than 25
are at greater risk than younger individuals.
Although a history of sugar in the urine is often
included in the list of risk factors, this is not a
reliable indicator of who will develop diabetes
during pregnancy. Some pregnant women with perfectly
normal blood sugar levels will occasionally have
sugar detected in their urine.
The Council on Diabetes in Pregnancy of the American
Diabetes Association strongly recommends that all
pregnant women be screened for gestational diabetes.
Several methods of screening exist. The most common
is the 50?gram glucose screening test. No special
preparation is necessary for this test, and there is
no need to fast before the test. The test is
performed by giving 50 grams of a glucose drink and
then measuring the blood sugar level l?hour later. A
woman with a blood sugar level of less than 140
milligrams per deciliter (mg/dl) at l?hour is
presumed not to have gestational diabetes and
requires no further testing. If the blood sugar
level is greater than 140 mg/dl the test is
considered abnormal or ?positive:? Not all women
with a positive screening test have diabetes.
Consequently, a 3?hour glucose tolerance test must
be performed to establish the diagnosis of
gestational diabetes.
If your physician determines that you should take
the complete 3?hour glucose tolerance test, you will
be asked to follow some special instructions in
preparation for the test. For 3 days before the
test, eat a diet that contains at least 150 grams of
carbohydrates each day. This can be accomplished by
including one cup of pasta, two servings of fruit,
four slices of bread, and three glasses of milk
every day. For 10 to 14 hours before the test you
should not eat and not drink anything but water. The
test is usually done in the morning in your
physician's office or in a laboratory. First, a
blood sample will be drawn to measure your fasting
blood sugar level. Then you will be asked to drink a
full bottle of a glucose drink (100 grams). This
glucose drink is extremely sweet and occasionally
makes some people feel nauseated. Finally, blood
samples will be drawn every hour for 3 hours after
the glucose drink has been consumed. The normal
values for this test are shown in table 1.
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From 752
Unselected Pregnancies
*O'Sullivan, J. B. Establishing Criteria for
Gestational Diabetes. Diabetes Care 3: 437?439,
1980.
If two or more of your blood sugar levels are higher
than the diagnostic criteria, you have gestational
diabetes. This testing is usually performed at the
end of the second or the beginning of the third
trimester (between the 24th and 28th weeks of
pregnancy) when insulin resistance usually begins.
If you had gestational diabetes in a previous
pregnancy or there is some reason why your physician
is unusually concerned about your risk of developing
gestational diabetes, you may be asked to take the
50?gram glucose screening test as early as the first
trimester (before the 13th week). Remember, merely
having sugar in your urine or even having an
abnormal blood sugar on the 50?gram glucose
screening test does not necessarily mean you have
gestational diabetes. The 3?hour glucose tolerance
test must be abnormal before the diagnosis is made.
How does gestational diabetes affect pregnancy
and will it hurt my baby?
The complications of gestational diabetes are
manageable and preventable. The key to prevention is
careful control of blood sugar levels just as soon
as the diagnosis of gestational diabetes is made.
You should be reassured that there are certain
things gestational diabetes does not usually cause.
Unlike Type I diabetes, gestational diabetes
generally does not cause birth defects. For the most
part, birth defects originate sometime during the
first trimester (before the 13th week) of pregnancy.
The insulin resistance from the contra?insulin
hormones produced by the placenta does not usually
occur until approximately the 24th week. Therefore,
women with gestational diabetes generally have
normal blood sugar levels during the critical first
trimester.
One of the major problems a woman with gestational
diabetes faces is a condition the baby may develop
called ?macrosomia.? Macrosomia means ?large body?
and refers to a baby that is considerably larger
than normal. All of the nutrients the fetus receives
come directly from the mother's blood. If the
maternal blood has too much glucose, the pancreas of
the fetus senses the high glucose levels and
produces more insulin in an attempt to use the
glucose. The fetus converts the extra glucose to
fat. Even when the mother has gestational diabetes,
the fetus is able to produce all the insulin it
needs. The combination of high blood glucose levels
from the mother and high insulin levels in the fetus
results in large deposits of fat which causes the
fetus to grow excessively large, a condition known
as macrosomia. Occasionally, the baby grows too
large to be delivered through the vagina and a
cesarean delivery becomes necessary. The
obstetrician can often determine if the fetus is
macrosomic by doing a physical examination. However,
in many cases a special test called an ultrasound is
used to measure the size of the fetus. This and
other special tests will be discussed later.
In addition to macrosomia, gestational diabetes
increases the risk of hypoglycemia (low blood sugar)
in the baby immediately after delivery. This problem
occurs if the mother's blood sugar levels have been
consistently high causing the fetus to have a high
level of insulin in its circulation. After delivery
the baby continues to have a high insulin level, but
it no longer has the high level of sugar from its
mother, resulting in the newborn's blood sugar level
becoming very low. Your baby's blood sugar level
will be checked in the newborn nursery and if the
level is too low, it may be necessary to give the
baby glucose intravenously. Infants of mothers with
gestational diabetes are also vulnerable to several
other chemical imbalances such as low serum calcium
and low serum magnesium levels.
All of these are manageable and preventable
problems. The key to prevention is careful control
of blood sugar levels in the mother just as soon as
the diagnosis of gestational diabetes is made. By
maintaining normal blood sugar levels, it is less
likely that a fetus will develop macrosomia,
hypoglycemia, or other chemical abnormalities.
What can be done to reduce problems associated
with gestational diabetes?
In addition to your obstetrician, there are other
health professionals who specialize in the
management of diabetes during pregnancy including
internists or diabetologists, registered dietitians,
qualified nutritionists, and diabetes educators.
Your doctor may recommend that you see one or more
of these specialists during your pregnancy. In
addition, a neonatologist (a doctor who specializes
in the care of newborn infants) should also be
called in to manage any complications the baby might
develop after delivery.
One of the essential components in the care of a
woman with gestational diabetes is a diet
specifically tailored to provide adequate nutrition
to meet the needs of the mother and the growing
fetus. At the same time the diet has to be planned
in such a way as to keep blood glucose levels in the
normal range (60 to 120 mg/dl). Specific details
about diet during pregnancy are discussed later.
An obstetrician, diabetes educator, or other health
care practitioner can teach you how to measure your
own blood glucose levels at home to see if levels
remain in an acceptable range on the prescribed
diet. The ability of patients to determine their own
blood sugar levels with easy?to?use equipment
represents a major milestone in the management of
diabetes, especially during pregnancy. The technique
called ?self blood glucose monitoring? (discussed in
detail later) allows you to check your blood sugar
levels at home or at work without costly and
time?consuming visits to your doctor. The values of
your blood sugar levels also determine if you need
to begin insulin therapy sometime during pregnancy.
Short of frequent trips to a laboratory, this is the
only way to see if blood glucose levels remain under
good control.
(From National Institute of Health)