Do We Know How to Find
Gestational Diabetes Mellitus?
1
Pathophysiology
Current Diagnosis Guideline
Discrepancies
2
Gestational Diabetes Mellitus (GDM)
A carbohydrate intolerance of varying
degrees and severity with onset or first
recognition during pregnancy with a
probable resolution after the end of
pregnancy. Diabetes, glucose intolerance
or insulin resistance may have existed
before the pregnancy.
3
Pregnancy Pathophysiology
Insulin resistance occurs because the hormonal
changes associated with pregnancy partially
block the effects of insulin.
Insulin resistance causes glucose to be shunted
from the mother to the fetus to facilitate fetal
growth and development.
During the third trimester of pregnancy, insulin
resistance increases by 50%.
4
Pregnancy Pathophysiology
Maternal pancreatic beta cells increase insulin
secretion almost 3 fold to compensate for
increased insulin resistance.
If the mother’s pancreas is unable to produce
sufficient insulin to overcome insulin resistance,
maternal glucose levels increase and GDM
occurs.
GDM usually disappears after pregnancy
because the hormonal changes that caused
insulin resistance are no longer present.
5
Management
Medical Nutrition therapy: nutrition
restriction and reconstruction
Insulin Therapy
6
Value of Laboratory Screening for GDM
Screening, identification and treatment can
decrease the morbidity and mortality of GDM.
Decreased macrosomia, cesarean birth and birth
trauma due to a > 4000g infant.
Decreased neonatal hypoglycemia, hypocalcemia,
hyperbilirubinemia, polycythemia.
Identify women at future risk for diabetes and those
with insulin resistance.
7
Demographics of GDM
Most common medical complication of
pregnancy
The prevalence may range from 1 to 14%
of all pregnancies, depending on the
population studied and the diagnostic tests
employed.
8
Who Should be Screened
Low-risk Group:
Requires no glucose testing, but this category is
limited to those women meeting all of the
following characteristics:
Age <25 years
Weight normal before pregnancy
Member of an ethnic group with a low prevalence
of GDM
No known diabetes in first-degree relatives
No history of abnormal glucose tolerance
No history of poor obstetric outcome
9
Who Should be Screened
High Risk Group:
Should undergo glucose testing as soon as
feasible. If they are found not to have GDM at
that initial screening, they should be retested
between 24 and 28 weeks of gestation.
Marked obesity
Personal history of GDM
Glycosuria
A strong family history of diabetes
10
Who Should be Screened
Women of average risk should have testing
undertaken at 24–28 weeks of gestation.
11
Screening
Fasting plasma glucose > 7.0 mmol/l(126 mg/dl)
Casual plasma glucose
> 11.1 mmol/l(200 mg/dl)
Diabetes
12
Fasting plasma glucose < 7.0 mmol/l(126 mg/dl)
Casual plasma glucose
< 11.1 mmol/l(200 mg/dl)
Two-step or one-step screening
approach
1. Glucose Challenge Test (GCT)
2. Oral Glucose Tolerance Test (OGTT)
13
Two-Step Screening
50g glucose challenge test (GCT)(non-fasting)
1hr
If glucose level < 7.2-7.8mmol/l (130-140mg/dl)
No further screening needed.
If >7.2-7.8mmol/l, proceed to diagnostic oral
glucose tolerance test (OGTT).
Nearly 25 % of women will have a + 1hr GCT, and will
need a OGTT.
14
One-Step Screening
Directly proceed to diagnostic oral glucose
tolerance test (OGTT).
The one-step approach may be cost-effective in high-risk
patients or population.
15
3-hr 100-g OGTT
16
2-hr 75-g OGTT
9.9
8.1
17
Skepticism
Developed in different population
Should we use the same cutoff concentrations?
2 out of 3 or 2 out of 4 thresholds?
18
19
Flow Chart of Study
Design
Pregnant women (16-20 weeks) (1017)
Perform 75g test
#227
g>7.2 mmol/l at 1hr
Perform 100g test
(17-21 weeks)
#45 GDM.
No further testing
#182 non-GDM.
#790 with g<7.2mmol/l at 1hr
#972 pregnant women (26-30 weeks)
Perform 75g test
#484 with g>7.2mmol/l at 1hr
Perform 100g test (27-31 weeks)
#488 with g<7.2mmol/l at 1hr
No further testing
20
21
Number of diagnosed GDM
100g test
16-21 weeks
pregnancy
26-31 weeks
pregnancy
75g test
41
15
30
4
60
26
49
15
Both
11
Cohen  index
11
P<0.001
0.21
0
0–0.2
0.2– 0.4
0.4 –0.8
0.8 –1.0
0.18
McNemar
disagreement
weak agreement
fair agreement
good agreement
perfect agreement
P<0.001
22
23
24
Different Approaches
Mixed meal tolerance tests
The area under the curve of a continuous
glucose profile for 3 h
Continuous glucose monitoring in the
typical home setting for several days
Something other than glucose?
25
What test best identifies
glucose toxicity for the fetus?
26