Gestational Diabetes Mellitus, a common pregnancy condition. KKH shares about diagnosis, risk and treatment for gestational diabetes mellitus.
Gestational Diabetes Mellitus (GDM) is a condition in which the body does not produce
enough of the hormone insulin to control sugar levels during pregnancy. It is a common
complication of pregnancy ranging from 10% to 20% of all pregnant women in Singapore.
WHAT ARE THE RISKS OF GESTATIONAL DIABETES MELLITUS?
GDM puts both mother and child at serious risks. The baby
can have excessive weight gain (also known as macrosomia)
and hypoglycaemia (low blood sugar) after birth, develop fetal
abnormalities, and even succumb to sudden fetal death.
The mother can develop high blood pressure and preeclampsia
while pregnant, give birth prematurely and run the
risk of getting Type 2 Diabetes Mellitus (DM) in her lifetime.
HOW TO DETECT GESTATIONAL DIABETES MELLITUS?
Screening for all pregnant women during pregnancy is
the most effective way to detect and manage it early. The
screening test for GDM is a three-point Oral Glucose Tolerance
Test (OGTT).
After fasting overnight, the woman’s blood is taken and
tested at three time-points at:
- Starting (Fasting); one hour; two hours after taking
a flavoured sweet drink calibrated at 75-gram glucose
load.
Any blood sugar levels above a certain criteria value for each
of the three time-points is considered GDM. The criteria for
each of the time-points are derived from an international
study (HAPO Study) of which KK Women’s and Children’s
Hospital (KKH) is one of the 15 main study centres.
WHEN IS THE BEST TIME TO DO OGTT?
The routine screening for GDM for pregnant women is best
performed at 24 to 28 weeks. However, if there are any risk
factors, e.g., persistent sugar in the urine or previous history
of GDM on insulin, the screening may be done earlier.
WHAT IS THE TREATMENT FOR GESTATIONAL DIABETES MELLITUS?
The treatment of GDM varies, depending on the result of the
OGTT. If the condition is mild, controlling the diet is often
enough. For more severe cases, oral medications (metformin)
or insulin injections (depending on severity) may be required
for the remainder of the pregnancy.
A dietitian will advise on a sensible eating plan, which is to
have a healthy diet and foods with a low glycaemic index.
Regular exercise (such as walking for 30 minutes after a meal)
to improve glycaemic control is recommended. Women with
GDM should have regular monitoring of fetal growth and deliver
by full-term.
WHAT FOLLOW-UP ACTION IS REQUIRED AFTER
DELIVERY FOR WOMEN WITH GDM DURING
PREGNANCY?
Women with GDM should be encouraged and supported
to breastfeed as breastfeeding reduces risk of
obesity and diabetes in the children. The dose of metformin,
glibenclamide and/or insulin may be reduced or
stopped after birth as indicated.
A repeat OGTT (two-point test) should be performed
6 weeks after delivery, with a follow-up in the clinic to
ensure that the high sugar level has resolved. This can
exclude existing Type 2 DM and will also identify women
with impaired glucose tolerance, for whom referral
for more active follow-up and intervention is required.
Even if the postnatal OGTT is normal, women with
a history of GDM should be informed about the increased
risk of developing Type 2 DM in her lifetime
and hyperglycaemia in subsequent pregnancies, and
should be offered lifestyle advice that includes weight
control, diet and exercise.
Women with background risk factors (e.g., obesity,
strong family history of Type 2 DM, insulin required during
pregnancy, metabolic syndrome etc.) should have
more frequent screening (yearly) than those at lower risk
(once every 2 to 3 years).
WHY IS IT IMPORTANT TO FOLLOW UP AFTER
DELIVERY?
Although GDM resolves in most women after their pregnancy,
these women still have a much higher risk of developing
Type 2 DM in their lifetime. Type 2 DM, if not detected early or not well-controlled, can be associated with permanent
complications to the kidneys, eyes and blood vessels.
There is evidence that certain lifestyle changes to diet and
exercise can help delay or even prevent the development of
Type 2 DM after GDM. Follow-up after delivery is therefore
important for detecting persisting or the onset of Type 2 DM,
in order to achieve prompt and optimal control and treatment
of the condition.
WHAT ARE THE MEASURES TO REDUCE THE FUTURE
RISK OF TYPE 2 DM?
The main ways to reduce the risk of developing Type 2 DM
after GDM are sensible eating and regular exercise, both
of which contribute to reducing body weight and Body Mass
Index (BMI). A high BMI is associated with an increased risk of
developing Type 2 DM.
Weight loss should be slow, steady and sustained. The recommended
rate of weight loss is 0.5 to 1kg per week. A reduction
of 7% body weight in 6 months is a safe and effective
weight loss goal.
GPs can call for appointments through the KKH Central Appointments Hotline
at 6294 4050 for more information.
By: Professor Tan Kok Hian, Head and Senior Consultant, Perinatal Audit and Epidemiology Unit, Division of Obstetrics and Gynaecology, KK Women’s and Children’s Hospital
Professor Tan Kok Hian is the Head and Senior Consultant of the Perinatal Audit and
Epidemiology Unit, Department of Maternal Fetal Medicine, KK Women’s and Children’s
Hospital (KKH). Professor Tan is also the Lead for Gestational Diabetes Mellitus
(GDM) at the SingHealth Duke-NUS Diabetes Centre and the Lead Principal Investigator
of the NMRC-funded Integrated Platform for Research in Advancing Metabolic
Health Outcomes of Women and Children (IPRAMHO).
Professor Tan initiated universal screening for GDM, and the new International Association
of Diabetes and Pregnancy Study Groups criteria, in KKH and Singapore
General Hospital since January 2016 - based on a cost-effectiveness study of GDM
screening under the Growing Up towards Healthy Outcomes (GUSTO) study. He is also
the Chairperson of the College of Obstetricians and Gynaecologists, Singapore GDM
Committee 2017-2018 and Chairperson, Expert Group GDM Appropriate Care Guide
of the Agency for Care Effectiveness, Ministry of Health 2017-2018.
References
1. Tan KH, Tan T, Chi C, Thian S, Tan LK, Yong TT. Guidelines for the Management of Gestational Diabetes Mellitus. College of Obstetricians
and Gynaecologists, Singapore. Singapore Journal of Obstetrics & Gynaecology. 2018; 49(1):9-13
2. Chen PY, Finkelstein EA, Ng MJ, Yap F, Yeo GS, Rajadurai VS, Chong YS, Gluckman PD, Saw SM, Kwek KY, Tan KH. Incremental Cost-Effectiveness
Analysis of Gestational Diabetes Mellitus Screening Strategies in Singapore. Asia-Pacific Journal of Public Health 2016; 28(1):15-25
3. Chong YS, Cai S, Lin H, Soh SE, Lee YS, Leow MK, Chan YH, Chen L, Holbrook JD, Tan KH, Rajadurai VS, Yeo GS, Kramer MS, Saw SM,
Gluckman PD, Godfrey KM, Kwek K; GUSTO study group. Ethnic differences translate to inadequacy of high-risk screening for gestational
diabetes mellitus in an Asian population: a cohort study. BMC Pregnancy Childbirth. 2014 Oct 2;14:345
4. HAPO Study Cooperative Research Group Hyperglycemia and adverse pregnancy outcomes. N Engl J Med. 2008 May 8;358(19):1991-
2002.
