![]()
SA JOURNAL OF DIABETES & VASCULAR DISEASE
REVIEW
VOLUME 8 NUMBER 2 • JUNE 2011
55
• past obstetric history of GDM
• first-degree relative with diabetes
• ethnic group with high prevalence of diabetes: south Asian
(specifically women whose country of origin is India or Pakistan),
black Caribbean and Middle Eastern.
Pregnant women who have one risk factor should be offered
screening for GDM.
2
It is important to note that up to 50% of
women with GDM do not have any identifiable risk factors.
11
Gestational diabetes screening
Controversy abounds regarding the appropriate screening method
for gestational diabetes. The major controversy surrounds whether
the screening should be directed or universal. Cost efficacy is a large
component of groups who propose directed or targeted screening.
Following on the HAPO trial, the International Association of
Diabetes and Pregnancy study groups (IADPSG) consensus panel
has made the proposal for international criteria for the diagnosis of
GDM and overt diabetes
11,12
(Table 2). The consensus statement has
been made ‘because associations (from HAPO) were continuous
with no obvious thresholds at which risks were increased’.
12
The IADPSG strategy for detection of diabetes in pregnancy
(either overt or GDM) is in two steps:
12
Step 1: Measure fasting plasma glucose (FPG), HbA
1c
or random
plasma glucose on all women or only high-risk women. If values
are diagnostic of overt diabetes (as above), treat as pre-existing
diabetes. If FPG
≥
5.1 mmol/l and
≤
7 mmol/l, then treat as GDM.
Step 2: If FPG
≤
5.1 mmol/l then screen for GDM at between 24
and 28 weeks (see above for proposed diagnostic criteria).
The IADPSG does concede that this would most likely drastically
increase the number of women diagnosed with GDM, with its
associated management costs. They feel that this is justified given
the prevalence of obesity worldwide.
12
A recent study by Finnish
authors, Kolu
et al
. found the costs associated with antenatal care
for GDM to be 10 to 41% more than for the low-risk antenatal
population. The author concluded that ‘primary health care is
needed to reduce special health care costs related to GDM’.
13
Advantages of the IADPSG strategy are that the values are linked to
adverse pregnancy outcome, overt diabetes should be diagnosed
early (if patients book within the first trimester or early second
trimester of pregnancy) and, most importantly, they promote
international standardisation for the diagnosis of GDM and overt
diabetes in pregnancy.
14
This approach should diagnose up to 18% of women with
GDM.
12,14
This is important to note for resource-constrained areas
such as South Africa. As suggested by the Australasian Diabetes
in Pregnancy Society (ADIPS) where resources are constrained,
selective screening may be utilised.
8,15
The American Diabetes Association (ADA)
16
suggests risk
categorisation for all pregnant women at the first visit. In high-risk
patients, a glucose tolerance test is administered. In average-risk
or high-risk (with negative early GTT) women, a GTT at 24 to 28
weeks gestation is required. Low-risk women do not require testing
at all during pregnancy.
8
These criteria for low risk are:
• maternal age
≤
25 years
• normal BMI
• negative family history of diabetes
• no history of abnormal glucose metabolism
• no previous poor obstetric outcome
• non-high-risk ethnic group.
The crux of the difference between the IADPSG strategy and other
methods is that the other methods’ screening values are based
on data predicting the risk of developing diabetes long term or
the criteria for glucose tolerance disorders in the non-pregnant
population.
14
HAPO has shown that this approach will lead to
increased adverse pregnancy outcomes: large-for-gestational-
age (LGA) foetuses and the attendant morbidity and mortality,
increased caesarean section rate, pre-term births and increased
NICU admissions.
10
The question that needs to be posed is whether treatment of
GDM reduces peri-natal morbidity. The Australian Carbohydrate
Intolerance Study in Pregnant Women (ACHOIS) trial has shown
that serious peri-natal morbidity is reduced when GDM is treated.
17
The literature is currently silent on whether diagnosis and treatment
of GDM from 24 to 28 weeks gestation will be of benefit to the
foetus long term.
14
GDM and maternal health
The presence of gestational diabetes mellitus has been shown to
increase the maternal risk of type 2 diabetes by up to 9.6 times.
There is also a strong association between GDM and cardiovascular
disease.
14
Therefore diagnosis of GDMpresents a unique opportunity
for healthcare professionals to identify women at high risk of type
2 diabetes and cardiovascular disease and institute preventative or
treatment measures.
14
GDM and long-term foetal health
It is known that babies born to mothers with GDM themselves have
an increased risk of the metabolic syndrome and type 2 diabetes in
their later life.
14
The quandary is that currently the best treatment
option(s) to reduce or eliminate the latter risks elude us at this point
in time.
14
Treatment of GDM
Once the diagnosis of GDM has been made, intensive counselling
of the patient must be done. The counselling must cover the risks
associated with the diagnosis of GDM (for mother and baby):
2
• support services for any adverse consequences following the
diagnosis of GDM (e.g. psychological support for anxiety and
depression)
• the lifestyle adjustments that must be made (exercise)
2
• dietary adjustments (reduction in caloric intake if BMI
≥
27 kg/m
2
)
2
Table 2.
IADPSG proposed criteria for GDM or overt diabetes in
pregnancy.
11,12
Hyperglycaemia during pregnancy
Gestational diabetes
*
Fasting plasma glucose
≥
5.1 mmol/l
1-hour plasma glucose
≥
10.0 mmol/l
2-hour plasma glucose
≥
8.5 mol/l
Overt diabetes in pregnancy
Fasting plasma glucose
≥
7.0 mmol/l
HbA
1c
≥
6.5% (DCCT/UKPDS standardised)
Random plasma glucose
≥
11.1 mmol/l and confirmed by either fasting
plasma glucose or HbA
1c
*One or more of these values after a 75-g OGTT is consistent with GDM.
