Introduction
Thirty percent of Goulburn Valley Health’s
pregnant population have a Body Mass Index (BMI) > or >30 kg/ m2
(1) putting them at 1.4 times the risk of type 2 diabetes
(T2DM) (2). It is described as one of the most challenging public health
problems of the 21st century (2) .
Symptoms of type 2 diabetes have insidious onset(3) with many people undiagnosed for years before clinical symptoms
arise (4). A review of available literature suggests many women are diagnosed
on their first antenatal visit(4) but are then “misdiagnosed” with gestational diabetes (4, 5) .Gestational
diabetes affects four percent of the obstetric population (6) but the degree of risk it poses to pregnancy outcomes is
controversial. This controversy leads differences in management of diabetes
during pregnancy with calls for uniformity of approach to care (6) . It is also preventing the diagnosis of T2DM putting women and
their babies at increased risk of serious outcomes to their pregnancies.
Prevalence
Overweight and obesity are common in the
obstetric population (7) thirty percent of Goulburn Valley’s pregnant population are
confirmed as obese (1) . The prevalence of
undiagnosed diabetes in the rural population in the state of Victoria, in one
study was found to be 26.3%(8) . In this study 1454 men and women aged 25 years and older were
randomly selected from six rural towns and assessed for diabetes This study
demonstrated that the prevalence of diabetes had doubled in the last 15 years.
The study doesn’t distinguish between T2DM and type 1 diabetes mellitus but it
is unlikely that a person can remain undiagnosed with type 1 diabetes mellitus
for any length of time. T2DM is no
longer confined to the older population. It is suggested that the prevalence of
T2DM is on the increase in the young, non pregnant population (9). This can lead us to wonder about the true prevelance in the
pregnant population. A recent survey of 180 births in Australia reported that
fifty five percent occurred in women with type 2 diabetes (10).
The risks of T2DM in pregnancy
In the past
physicians and women have thought of T2DM as a lower risk condition than
type 1 diabetes (11, 12) .
This thought has been carried through to the management of T2DM in pregnant
women.
MATERNAL RISKS OF T2DM
|
EARLY PREGNANCY RISK
|
LATE PREGNANCY RISK
|
NEONATAL RISK
|
CHILDHOOD RISK
|
Miscarriage
|
||||
|
(Cardiac
& Muscoskeletal abnormalities)
|
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Looking at the table above it would be
reasonable to agree with Melamed and Hod in their review of perinatal mortality
in pregestational diabetes,when they state that the management of T2DM should
be the same as type 1 diabetes (12) .
At risk groups
There has yet to be an agreement as to
whether all pregnant women should be screened for T2DM at the first antenatal
visit or whether screening should be confined to those who are at particular
risk.
Women that should be considered ‘at risk’
of undiagnosed type 2 diabetes are those with a BMI >30kg/m2 (18, 19).
Screening method
The choice of screening method in pregnancy
is a problem; the oral glucose tolerance test (OGTT) is defined as the ‘gold
standard’ test by the World Health Organisation (WHO) (20) however, it is not easily tolerated by women in early pregnancy due
to nausea and vomiting. Borch-Johnsen of
the diabetes centre Copenhagen argues there is no ‘gold standard’ and different
tests identify different subjects (21) .The WHO is currently reviewing the possibility of using the HbA1c
blood test yet the HbA1c test as a diagnostic tool for type 2 diabetes in pregnancy is questionable.
Arguments against the HbA1c
- Measurement
of HbA1c is not yet standardized around the world and has significant
biological variation in non-diabetic subjects. There is currently
insufficient evidence to enable a judgment to be made regard to its
performance as a screening test.
- Not
commonly used amongst the ordinary population as a screening test
- Affected
by anaemia – therefore affected by physiology of pregnancy
- What
level should be used
- HbA1c
level is significantly lower in early and in late pregnancy
- More
expensive
- Already
determined to be inappropriate for gestational diabetes
- HbA1c
results differ in different ethnicities
- Uniformity
of laboratory testing is required
Arguments for the HbA1c
- less affected
by stress
- no
fasting
- More
sensitive
- Not
affected by diet
- One blood
test
- Less time
consuming
- Better
index of overall glycaemic exposure and risk for longterm complications
Evidence of HbA1c use in pregnancy
- Level
setting at 5.3
- Erythocyte
turnover repeat the test every 3-4 wks
- HbA1c
cannot be used to predict fetal size and birth weight
Discussion
Detection of type 2 diabetes in pregnancy
is worthwhile because there is a need to differentiate between women suffering
from undiagnosed type 2 diabetes and women with gestational diabetes. Women who’s pregnancies are complicated by
type 2 diabetes are suffering a more severe disease associated with
longstanding glucose intolerance with the risk of major malformations in the
developing fetus due to uncontrolled hypergycaemia. The risk of uncontrolled hyperglycaemia is
greater in those women who are yet to be diagnosed but who will be entering
their first trimester of pregnancy. Diabetes diagnosed in early pregnancy has
graver consequences and needs to be addressed as soon as possible (22) .
·
Primary caesarean section rate
could be reduced.
·
Education and lifestyle
management plans can be put in place to prevent the development of the
complications of type 2 diabetes.
Conclusion:
Screening for type 2 diabetes in pregnancy
should be considered in women who are high risk.
Women already pregnant and considered to be
at high risk of undiagnosed type 2 diabetes need to be offered earlier
appointments at antenatal booking clinics with a midwife who specialises in
diabetes.
What needs urgent consideration is whether
opportunistic screening of women in the primary care setting should take place
for women considered at increased risk of undiagnosed T2DM. Another option may
be exploring the cost effectiveness of offering a midwife led preconception
clinic to screen for T2DM in high risk women planning to become pregnant.
Further research is needed to look at HbA1c
as a diagnostic tool for undiagnosed type two diabetes in early pregnancy with
follow up of women tested through their pregnancies looking at foetal growth,
birth outcome and birth weight. The women tested should then be followed up
following pregnancy to confirm or deny type 2 diabetes at 3 months post partum.
References
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