in pregnancy, where there are two types--hypertension coincidental with
pregnancy and hypertension because of pregnancy (PIH), there are two types
of diabetes that can be present in pregnancy: Gestational Diabetes
and Insulin Dependent Diabetes Mellitus (IDDM). There is also a combination
of the two in which IDDM is just harder to control because of a gestational
diabetes overlay.
Gestational Diabetes
Pregnancy causes a phenomenon
called "insulin resistance," which for lack of a better explanation means
that a pregnant woman makes insulin--it's just that it's lousier insulin.
It doesn't react to receptors at the cellular level as well, meaning it
takes more of it to do what insulin is supposed to do-¡Vbring sugar into
the cells for energy. Being overweight makes this worse. In pregnancy,
when the insulin made just can't do the job anymore, we call this GDM (Gestational
Diabetes Mellitus). Since the insulin isn't as powerful, a diet low
in sugar and carbohydrates will mean less sugar in the system; less sugar
in the system means less left over from the faulty insulin chemistry.
This is what is meant by diet-controlled gestational diabetes and actually
works fairly well with this condition.
Because diet does work
well, very few women need insulin injections with GDM. As many as
1 out of 10 - 20 pregnancies will have GDM. It used to be a sneaky
disease until we started screening all pregnancies with the O'Sullivan
test (a 1-hour blood glucose determination after a sugar drink).
Out of those with an abnormal test, a full 3-hour glucose tolerance test
(a fasting, followed by 3 subsequent sugar determinations after a sugar
drink) will then pick out the real GDM patients. GDM can have the same complication as "regular" diabetes--large
babies, so it is important to manage it aggressively.
And then there are the "real"
diabetics.
Diabetes Mellitus
This isn't making insulin
that is lackluster, but actually not making enough insulin at all.
When there isn't enough insulin tobring sugar from the blood stream (your blood
stream is what you eat) into the tissue, it builds up in the blood stream,
gunking up the works. This leads to damage of the blood supply to
one's organs, resulting in kidney damage, eye damage, etc.
Women who are diabetic
when they conceive are at twice the risk for abnormal fetuses, even when
their blood sugars are well controlled. (But even with this doubled risk,
the chances of having a baby with congenital abnormalities is only 4 -5
out of a hundred.)
But diabetic women who
have blood sugars that aren't well controlled have a staggering increase
in their risk-¡Vby about ten times what their normal risk would be for a well-controlled
diabetic state. So the real deal-breaker here is good control before
conception. Luckily, there's a test that can tell how well the diabetes
has been controlled. It is called a HbA1c (Hemoglobin A1C) and measures
how much sugar is "stuck" to a certain hemoglobin molecule. The beauty
of this relationship between hemoglobin and glucose is that it's a firm
interaction-¡Vmeaning that it reflects how well the diabetes has been in
control for a long time, usually months.
So a normal HbA1c in
the first trimester will be a very reassuring test for a pregnant diabetic
patient. And the risk of congenital abnormalities and miscarriage
is directly related to how abnormally high the HbA1c is. This makes
it, besides the serum glucose measurement, the most important prenatal
(and preconception!) test in diabetic pregnancy.
But even with good control
preconception and during the first trimester, the two natural enemies,
pregnancy and diabetes, begin to fight it out. The very thing that can
cause that normal variation known as GDM can make insulin-dependent diabetes
harder to manage, too, by driving up the insulin needs. This means
that no "set" dosage of insulin can be established with expectations of
the pregnancy sugar control to be on automatic pilot. It doesn't
work that way, and pregnancy + diabetes is usually a continuing medical challenge always
at red alert.
Large babies make for more
difficult vaginal deliveries. Besides the risk of cephalopelvic dysproportion
(baby's to big to fit out), and shoulder dystocia (head delivers but shoulders
get stuck), there is also increased risk of placental abruption premature
separation). Since the C-section rate is higher in diabetic patients
for all of the above reasons, it's important to know that Cesarean delivery
is not the perfect answer to a pregnant diabetic's problems. Diabetic
women don't heal well after surgery and their chances of infection are
much greater.
In spite of all of these
concerns, a woman whose sugars are well controlled can stack the deck in
her favor, especially if she is evaluated preconception. But diabetes
is a definite problem in pregnancy that requires diligence on the part
of the obstetrician and strict compliance on the part of the patient.
My baby is a little large on
ultrasound for the gestational age. My one-hour glucola test came back
elevated. Is this diabetes?
Certainly
LGA (large for gestational age) babies are a concern and make us think
of gestational diabetes. The one-hour glucola test (the O'Sullivan test)
is the screen for it. But because it's just a screen, it's only considered
valid (and reassuring) if it comes back normal. If it's elevated, we chunk
the results and move up to a better diagnostic test -- the full-blown Glucose
Tolerance Test (GTT), where you have a fasting sugar drawn, then you consume
a sugar load (possibly more glucola), then have blood sugars drawn at one,
two and three-hour intervals. There are blood sugar levels appropriate
for each blood sample in this test, and if you are too high in two of them,
you will be considered a gestational diabetic (up to 10 percent of pregnant
women can be).
Even if this happens, don't
panic. It is usually controlled with a diabetic diet -- a diet with a lot
of food on it, actually, but with just a shift in the types of things you
eat. Rarely do we need insulin. Gestational diabetes is not a real diabetes,
because it's not that you don't make enough insulin, it's just that the
insulin you make is not as good. We call this "insulin resistance." But
don't underestimate gestational diabetes -- it can cause bad effects on
the baby and you just like the real thing! Like...
Humongous babies that are at
a higher risk for complications of delivery like shoulder dystocia, and...More
likelihood of you needing a C-section. But if you were to have gestational
diabetes and were to be real good about your diet, you will likely avoid
these complications. Your doctor will watch for these concerns. But we're
getting ahead of ourselves. You only flunked the one-hour test. You
may very well pass the GTT with flying colors, in which case you're off
the hook.
By the way, the woman who
instituted the glucola test -- a test that has probably saved thousands
of lives by making often-silent gestational diabetes another aspect of
pregnancy to be treated -- Dr. O'Sullivan herself -- was one of my examiners
on my board exams. And she didn't ask me one single question about
diabetes!
How low should your blood sugar
be when you have gestational diabetes, and how does a doctor make this
diagnosis?
The protocol I use in my practice is if the O'Sullivan (glucola screen) test
is abnormal at 24 to 26 weeks, I then move up to the three-hour glucose
tolerance test. If two out of the four blood samples are abnormal, that's
when I make the diagnosis of gestational diabetes. If your doctor labeled
you as gestational diabetic on the glucola screen alone, he or she may
be using this technique to justify an ADA diet (American Diabetes Association).
It's jumping the gun, but there's no real harm here, especially if you're
continuing to test your sugars. Even if you were on such a diet and not
even diabetic, it's a nice diet for any pregnant woman, because there isn't
inappropriate weight gain on this diet. (It's not unlike the "Sugar-buster
Diet" my colleagues in New Orleans have developed.)
If foregoing the full glucose
tolerance test was a mistake, you'll see evidence of this on the blood
sugars you've been taking. (Perhaps your doctor was being sensitive to
not putting you through a major pain-in-the-behind test.)
How low is too low? A sugar
so low thatyou're dizzy, pass out, or become ill is toolow. If there are
no deleterious effects, a low blood sugar is not harmful to you or your
baby. (The baby takes all of the sugar it can and leaves the rest for you.)
