Pregestational Diabetes
Approximately 1% of all pregnant
patients are diabetic before pregnancy. Type 2 pregestational diabetes mellitus
is most common. Although 90% of diabetes
cases encounteredduring pregnancy are GDM, more than one half of these
even-tually develop type 2 pregestational diabetes mellitus later in life.
Women with pregestational
diabetes should receive an ultrasound examination early in pregnancy to check
for fetal viability and accurately date the gestational age. At 18 to 20 weeks
of gestation, an ultrasound examination that focuses on identification of
congenital anomalies, es-pecially those of the heart and great vessels, is
indicated. Echocardiography may also be done if there are suspected cardiac
defects or when the fetal heart and great vessels could not be visualized by
ultrasonography.
Antepartum
fetal monitoring, including fetal movement counting, the nonstress test,
biophysical profile, and contraction stress test, performed at appropriate
intervals, is a valuable approach and can be used to monitor women with
pregestational diabetes. This testing is usually initiated
at 32 to 34 weeksof gestation, but can be undertaken earlier if other high-risk
conditions exist.
Pregnant patients with
pregestational diabetes, especially type 1 diabetes, are at higher risk for
diabetic ketoacidosis (DKA), the management of which is not altered in
preg-nancy. Fetal death can accompany DKA, so electronic fetal monitoring is
essential until the maternal metabolic status is stabilized.
Hypoglycemia
may also occur periodically, especiallyearly in
pregnancy, when nausea and vomiting interfere with caloric intake. Although
hypoglycemia does not have adverse effects on the fetus, patients and family
should be taught how to respond quickly and appropriately to hypoglycemia.
In addition to the added
difficulties of glucose man-agement and the increased risk of DKA during
pregnancy, mothers with pregestational
diabetes have a two-fold increase in the incidence of pregnancy-induced
hypertension, or preeclamp-sia, compared
with patients without diabetes. Because of thisincreased risk of
preeclampsia, 24-hour urine collections to determine the level of proteinuria
and creatinine clear-ance are often used in pregestational diabetics.
Additionally, if patients have preexisting diabetic
nephropathy, man-ifested by pre-pregnancy creatinine >1.5 or severe pro-teinuria, they
are at an increased risk of progression to end-stage renal disease, and serial
monitoring of renal function is warranted.
Diabetic retinopathy worsens in approximately 15% of pregnant patients with
preexisting diabetes, some pro-ceeding to proliferative retinopathy and loss of
vision if the process remains untreated by laser coagulation. Therefore, women
with pregestational type 1 or type 2 diabetes should have an ophthalmologic
evaluation once in their first trimester if asymptomatic, and as needed if
symptoms arise.
The patient with long-standing
diabetes should realize that strict control of her glucose levels is advised
during pregnancy, with greater attention to and more frequent monitoring of
glucose values. For these patients,
manage-ment ideally begins before conception, with the goal of optimal glucose
control before and during pregnancy. Hemoglobin A1clevels can be
measured to reflect average glucose values over the preceding 12 weeks. These
levels can then be used to monitor glucose control both before and during
preg-nancy and to predict the likelihood of congenital anom-alies in the fetus.
Excellent glucose control is
achieved using a careful combination of diet, exercise, and insulin therapy. Insulinrequirements will increase throughout
pregnancy, most markedly in the period between 28 to 32 weeks of gestation.
The impact of pregnancy on
diabetes, and vice versa, must also be emphasized to the pregnant patient with
pre-gestational diabetes. Patients may need to be seen every 1 to 2 weeks
during the first two trimesters and weekly after 28 to 30 weeks of gestation.
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