The article on gestational diabetes
mellitus (GDM) in last
month's issue (The Female
Patient. 2011;36[4]:24-28)
should remind us that diabetes
mellitus is a significant problem in
the provision of care to women.
Most importantly, as health care
providers we have the opportunity,
including a long time frame, to intervene
and hopefully assist
women in modifying their risk factors
for this disorder.
This is particularly true for type
2 diabetes, which is characterized
by elevated blood glucose, insulin
resistance, and impairment of insulin
secretion. A case in point is
women who have had GDM. As
many as 20% of these women will
have some impairment of their
glucose tolerance in the postpartum
period, which emphasizes the
need to perform a 2-hour 75-g oral
glucose tolerance test on all
women with GDM at 6 to 12 weeks
after delivery.
A recent meta-analysis involving
20 cohort studies indicated that
women who had GDM had a relative
risk (RR) for type 2 diabetes of
7.43 (95% CI, 4.79-11.51), compared
to women without glucose intolerance
during pregnancy. This relative
risk increased as time went by,
reaching 9.34 after an interval of
more than 5 years since the
pregnancy.
How does this equate to an absolute
risk? Based on a Canadian
population-based study of about
22,000 women in Ontario who had
had GDM, the frequency of type 2
diabetes reached 13.1% at 5 years
postpartum and 18.9% by 9 years
postpartum. For comparison, the
rate of type 2 diabetes in women
who were normoglycemic with
their previous pregnancy was 2%.
For women who have had GDM,
as well as others with risk factors
for type 2 diabetes, there is some
evidence that lifestyle interventions
can be effective in delaying the
onset of diabetes and perhaps even
reducing the risk for cardiovascular
complications. Obesity is a major
risk factor for type 2 diabetes. For
example, among women who are
obese and who have had GDM, at
least 50% will develop type 2 diabetes.
Lifestyle preventive strategies
that have been shown to be effective
include weight loss and
exercise.
In a 2001 Finnish study of 522 patients
(mean age, 55; mean BMI,
33), the mean weight loss in a
weight-reduction and exercise
group versus a control group was
3.5 kg after 2 years. More importantly,
the intervention group had
an incidence of type 2 diabetes of
11%, compared to 23% in the control
group.
In the Diabetes Prevention Trial
published in 2002, 3 groups of
obese patients at high risk for diabetes
were compared: those on a
"lifestyle intervention" (intense
monitored diet and exercise program),
those receiving metformin
and information on diet and exercise,
and a group receiving information
on diet and exercise. After
about 3 years of follow-up, only 14%
of those on the lifestyle intervention
developed diabetes, compared
to 22% and 29% in the metformin
and information-only groups,
respectively.
An exercise program can independently
also reduce the risk for
diabetes. For example, a metaanalysis
of 10 prospective cohort
studies indicated that moderate exercise
reduced the risk for type 2 diabetes
by about 30% [RR 0.69 (95%
CI, 0.58-0.83)]. This effect may
occur despite other interventions,
since the benefit persisted when
the data were adjusted for BMI.
These findings have obvious implication
for our practices. Clearly,
all women at risk for diabetes
should be counseled regarding the
value of diet and exercise in the
maintenance of ideal body weight.
In particular, young women who
develop GDM and are overweight
or obese should be informed of the
risks for type 2 diabetes. In addition,
they need to know that type 2
diabetes is associated with an increased
risk for cardiovascular disease,
a risk that is higher in women
than in men. Further, adopting a
healthy lifestyle at this time will
also have a positive influence on
their children.
Finally, it should be noted there is
continuing interest in research of
pregnant women with GDM or at
significant risk for GDM to see if interventions
such as exercise in addition
to diet will improve outcomes.
Randomized clinical trials
of women with mild GDM have
shown improvement in clinical
outcomes, including reduced birth
weight and less preeclampsia,
when they were treated with diet
and exercise.
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Ronald T. Burkman, MD
Editor-in-Chief
SUGGESTED READING
Bellamy L, Casas JP, Hingorani AD, Williams D.
Type 2 diabetes after gestational diabetes: a
systematic review and meta-analysis. Lancet.
2009;373(9677):1773-1779.
Feig DS, Zinman B, Wang X, Hux JE. Risk of
development of diabetes mellitus after diagnosis
of gestational diabetes. CMAJ. 2008;179(3):
229-234.
Jeon CY, Lokken RP, Hu FB, van Dam RM. Physical
activity of moderate intensity and risk of
type 2 diabetes: a systematic review. Diabetes
Care. 2007;30(3):744-752.
Knowler WC, Barrett-Connor E, Fowler SE, et al.
Reduction in the incidence of type 2 diabetes
with lifestyle intervention or metformin. N Engl
J Med. 2002;346(6):393-403.
Landon MB, Spong CY, Thom E, et al. A multicenter,
randomized trial of treatment for mild
gestational diabetes. N Engl J Med. 2009;361(14):
1339-1348.
O'Sullivan JB. Diabetes mellitus after GDM.
Diabetes. 1991;40 Suppl 2:131-135.
Tuomilehto J, Lindstrom J, Eriksson JG, et al.
Prevention of type 2 diabetes mellitus by
changes in lifestyle among subjects with
impaired glucose tolerance. N Engl J Med.
2001;344(18):1343-1350.
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