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Undersetanding
Gestational Diabetes, Part II:
Glucose Monitoring
What
is self blood glucose monitoring?
Once you are diagnosed as having
gestational diabetes, you and your health care providers will want to
know more about your day-to-day blood sugar levels. It is important
to know how your exercise habits and eating patterns affect your blood
sugars. Also, as your pregnancy progresses, the placenta will release
more of the hormones that work against insulin. Testing your blood sugar
level at important times during the day will help determine if proper
diet and weight gain have kept blood sugar levels normal or if extra
insulin is needed to help keep the fetus protected.
Self
blood glucose monitoring is done by using a special device to obtain
a drop of your blood and test it for your blood sugar level. Your doctor
or other health care provider will explain the procedure to you. Make
sure that you are shown how to do the testing before attempting it on
your own. Some items you may use to monitor your blood sugar levels
are:
Lancet–a disposable, sharp needle-like sticker for pricking
the finger to obtain a drop of blood.
Lancet device–a spring -loaded finger-sticking device.
Test strip–a chemically treated strip to which a drop of blood
is applied.
Color chart–a chart used to compare against the color on the
test strip for blood sugar level.
Glucose meter–a device which “reads” the test strip and gives
you a digital number value.
Your health care provider can advise you where to obtain the self-monitoring
equipment in your area. You may want to inquire if any places rent or
loan glucose meters, since it is likely you won't be needing it after
your baby is born.
How often and when should I test?
You may need to test your blood
several times a day. Generally, these times are fasting (first thing
in the morning before you eat) and 2 hours after each meal. Occasionally,
you may be asked to test more frequently during the day or at night.
As each person is an individual, your health care provider can advise
the schedule best for you.
How should I record my test results?
Most manufacturers of glucose
testing products provide a record diary, although some health care providers
may have their own version. You should record any test result immediately
because it's easy to forget what the reading was during the course of
a busy day. You should always have this diary with you when you visit
your doctor or other health care provider or when you contact them by
phone. These results are very important in making decisions about your
health care.
Are there any other tests I should know about?
In addition to blood testing,
you may be asked to check your urine for ketones. Ketones are by-products
of the breakdown of fat and may be found in the blood and urine as a
result of inadequate insulin or from inadequate calories in your diet.
Although it is not known whether or not small amounts of ketones can
harm the fetus, when large amounts of ketones are present they are accompanied
by a blood condition, acidosis, which is known to harm the fetus. To
be on the safe side, you should watch for them in your urine and report
any positive results to your doctor.
How do I test for ketones?
To test the urine for ketones,
you can use a test strip similar to the one used for testing your blood.
This test strip has a special chemically treated pad to detect ketones
in the urine. Testing is done by passing the test strip through the
stream of urine or dipping the strip in and out of urine in a container.
As your pregnancy progresses, you might find it easier to use the container
method. All test strips are disposable and can be used only once. This
applies to blood sugar test strips also. You cannot use your blood sugar
test strips for urine testing, and you cannot use your urine ketone
test strips for blood sugar testing.
When do I test for ketones?
Overnight is the longest fasting
period, so you should test your urine first thing in the morning every
day and any time your blood sugar level goes over 240 mg/dl on the blood
glucose test. It is also important to test if you become ill and are
eating less food than normal. Your health care provider can advise what's
best for you.
Is it ever necessary to take insulin?
Yes, despite careful attention
to diet some women's blood sugars do not stay within an acceptable range.
A pregnant woman free of gestational diabetes rarely has a blood glucose
level that exceeds 100 mg/dl in the morning before breakfast (fasting)
or 2 hours after a meal. The optimum goal for a gestational diabetic
is blood sugar levels that are the same as those of a woman without
diabetes.
There
is no absolute blood sugar level that necessitates beginning insulin
injections. However, many physicians begin insulin if the fasting sugar
exceeds 105 mg/dl or if the level 2 hours after a meal exceeds 120 mg/dl
on two separate occasions. Blood sugar levels measured by you at home
will help your doctor know when it is necessary to begin insulin. The
ability to perform self blood glucose monitoring has made it possible
to begin insulin therapy at the earliest sign of high sugar levels,
thereby preventing the fetus from being exposed to high levels of glucose
from the mother's blood.
Will my baby be healthy?
The ultimate concern of any
expectant mother is, “Will my baby be all right?” There is an array
of simple, safe tests used to assess the condition of the fetus before
birth and these can be particularly valuable during a pregnancy complicated
by gestational diabetes. Tests that may be given during your pregnancy
include:
Ultrasound.
Ultrasound uses short pulses of high frequency, low-intensity sound
waves to create images. Unlike x-rays, there is no radiation exposure
to the fetus. First used during World War II to detect enemy submarines
below the surface of the water, ultrasound has since been used safely
in obstetrics. Occasionally, the date of your last menstrual period
is not sufficient to determine a due date. Ultrasound can provide an
accurate gestational age and due date that may be very important if
it is necessary to induce labor early or perform a cesarean delivery.
Ultrasound can also be used to determine the position of the placenta
if it is necessary to perform an amniocentesis (another test discussed
later).
Fetal movement records.
Recording fetal movement is a test you can do by yourself to help determine
the condition of the baby. Fetal activity is generally a reassuring
sign of well-being. Women are often asked to count fetal movements regularly
during the last trimester of pregnancy. You may be asked to set aside
specific times to lie down on your back or side and count the number
of times the baby moves or kicks. Three or more movements in a 2-hour
period are considered normal. Contact your obstetrician if you feel
fewer than three movements to determine if other tests are needed.
Fetal monitoring.
Modern instruments make it possible to monitor the baby's heart rate
before delivery. Currently, there are two types of fetal monitors —
internal and external. The internal monitor consists of a small wire
electrode attached directly to the scalp of the fetus after the membranes
have ruptured. The external monitor uses transducers secured to the
mother's abdomen by an elastic belt. One transducer records the baby's
heart rate by a sensitive microphone called a doppler. The other transducer
measures the firmness of the abdomen during a contraction of the uterus.
It is a crude measure of the strength and frequency of contractions.
Fetal monitoring is the basis for the non-stress test and the oxytocin
challenge test described below.
Non-stress test.
The “non-stress” test refers to the fact that no medication is given
to the mother to cause movement of the fetus or contraction of the uterus.
It is often used to confirm the well-being of the fetus based on the
principle that a healthy fetus will demonstrate an acceleration in its
heart rate following movement. Fetal activity may be spontaneous or
induced by external manipulation such as rubbing the mother's abdomen
or making a loud noise above the abdomen with a special device. When
movement of the fetus is noted, a recording of the fetal heart rate
is made. If the heart rate goes up, the test is normal. If the heart
rate does not accelerate, the fetus may merely be “sleeping”; if, after
stimulation, the fetus still does not react, it may be necessary to
perform a “stress test” (oxytocin challenge test).
Stress test (oxytocin challenge test).
Labor represents a stress to the fetus. Every time the uterus contracts,
the fetus is momentarily deprived of its usual blood supply and oxygen.
This is not a problem for most babies. However, some babies are not
healthy enough to handle the stress and demonstrate an abnormal heart
rate pattern. This test is often done if the non-stress test is abnormal.
It involves giving the hormone oxytocin (secreted by every mother when
normal labor begins) to the mother to stimulate uterine contractions.
The contractions are a challenge to the baby, similar to the challenge
of normal labor. If the baby's heart rate slows down rather than speeds
up after a contraction, the baby may be in jeopardy. The stress test
is considered more accurate than the nonstress test. Nevertheless,
it is not 100 percent foolproof and your obstetrician may want to repeat
it on another occasion to ensure its accuracy. Most women describe this
test as mildly uncomfortable but not painful.
Amniocentesis.
Amniocentesis is a method of removing a small amount of fluid from the
amniotic sac for analysis. Either the fluid itself or the cells shed
by the fetus into the fluid can be studied. In mid-pregnancy the cells
in amniotic fluid can be analyzed for genetic abnormalities such as
Down syndrome. Many women over the age of 35 have amniocentesis for
just this reason. Another important use for amniocentesis late in pregnancy
is to study the fluid itself to determine if the lungs of the fetus
are mature and able to withstand early delivery. This information can
be very important in deciding the best time for a woman with Type I
diabetes to deliver. It is not done as frequently to women with gestational
diabetes.
Amniocentesis
can be performed in an obstetrician's office or on an outpatient basis
in a hospital. For genetic testing, amniocentesis is usually performed
around the 16th week when the placenta and fetus can be located easily
with ultrasound and a needle can be inserted safely into the amniotic
sac. The overall complication rate for amniocentesis is less than 1
percent. The risk is even lower during the third trimester when the
amniotic sac is larger and easily identifiable.
Does gestational diabetes affect labor and delivery?
Most women with gestational
diabetes can complete pregnancy and begin labor naturally. Any pregnant
woman has a slight chance (about 5 percent) of developing preclampsia
(toxemia), a sudden onset of high blood pressure associated with protein
in the urine, occurring late in pregnancy. If preclampsia develops,
your obstetrician may recommend an early delivery. When an early delivery
is anticipated, an amniocentesis is usually performed to assess the
maturity of the baby's lungs.
Gestational
diabetes, by itself, is not an indication to perform a cesarean delivery,
but sometimes there are other reasons your doctor may elect to do a
cesarean. For example, the baby may be too large (macrosomic) to deliver
vaginally, or the baby may be in distress and unable to withstand vaginal
delivery. You should discuss the various possibilities for delivery
with your obstetrician so there are no surprises.
Careful
control of blood sugar levels remains important even during labor. If
a mother's blood sugar level becomes elevated during labor, the baby's
blood sugar level will also become elevated. High blood sugars in the
mother produce high insulin levels in the baby. Immediately after delivery
high insulin levels in the baby can drive its blood sugar level very
low since it will no longer have the high sugar concentration from its
mother's blood.
Women
whose gestational diabetes does not require that they take insulin during
their pregnancy, will not need to take insulin during their labor or
delivery. On the other hand, a woman who does require insulin during
pregnancy may be given insulin by injection on the morning labor begins,
or in some instances, it may be given intravenously throughout labor.
For most women with gestational diabetes there is no need for insulin
after the baby is born and blood sugar level returns to normal immediately.
The reason for this sudden return to normal lies in the fact that when
the placenta is removed the hormones it was producing (which caused
the insulin resistance) are also removed. Thus, the mother's insulin
is permitted to work normally without resistance. Your doctor may want
to check your blood sugar level the next morning, but it will most likely
be normal.
Should I expect my baby to have any problems?
One of the most frequently asked
questions is, “Will my baby have diabetes?” Almost universally the answer
is no. However, the baby is at risk for developing Type II diabetes
later in life, and of having other problems related to gestational diabetes,
such as hypoglycemia (low blood sugar) mentioned earlier. If your blood
sugars were not elevated during the 24 hours before delivery, there
is a good chance that hypoglycemia will not be a problem for your baby.
Nevertheless, a neonatologist (a doctor who specializes in the care
of newborn infants) or other doctor should check your baby's blood sugar
level and give extra glucose if necessary.
Another
problem that may develop in the infant of a mother with gestational
diabetes is jaundice. Jaundice occurs when extra red blood cells in
the baby's circulation are destroyed, releasing a substance called bilirubin.
Bilirubin is a pigment that causes a yellow discoloration of the skin
(jaundice). A minor degree of jaundice is common in many newborns. However,
the presence of large amounts of bilirubin in the baby's system can
be harmful and requires placing the baby under special lights which
help get rid of the pigment. In extreme cases, blood transfusions may
be necessary.
Will I develop diabetes in the future?
For most women gestational diabetes
disappears immediately after delivery. However, you should have your
blood sugars checked after your baby is born to make sure your levels
have returned to normal. Women who had gestational diabetes during one
pregnancy are at greater risk of developing it in a subsequent pregnancy.
It is important that you have appropriate screening tests for gestational
diabetes during future pregnancies as early as the first trimester.
Pregnancy
is a kind of “stress test” that often predicts future diabetic problems.
In one large study more than one-half of all women who had gestational
diabetes developed overt Type II diabetes within 15 years of pregnancy.
Because of the risk of developing Type II diabetes in the future, you
should have your blood sugar level checked when you see your doctor
for your routine checkups. There is a good chance you will be able
to reduce the risk of developing diabetes later in life by maintaining
an ideal body weight and exercising regularly.
A Practical
Guide to a Healthy Pregnancy
U.S. Department of Health and Human Services
Public Health Service National Institutes of Health
National Institute of Child Health
and Human Development
NIH Publication No. 93-2788
Reprinted February 1993
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