Welcome to the Diabetes e-Learning Suite.

Module 8:
Gestational Diabetes Mellitus

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Learning Objectives

After completing this module you should be able to:

Describe the epidemiological trend of gestational diabetes mellitus

Describe the clinical manifestation of gestational diabetes mellitus

Discuss screening methods for gestational diabetes mellitus

Describe the management of gestational diabetes mellitus

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 Gestational Diabetes Mellitus

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Prevalence of Hyperglycaemia in
Pregnancy

Women with hyperglycaemia during pregnancy is more prevalent in

low and middle-income countries

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Hyperglycaemia in Pregnancy:
Classification

• Women with slightly elevated blood

glucose levels
GDM
• Seems to occurs from 24 weeks of
pregnancy
Hyperglycaemia in Pregnancy

• Women with overt elevated blood

Diabetes mellitus in pregnancy
glucose levels

GDM: gestational diabetes mellitus.

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Epidemiology of GDM

Affects approximately 21 million live births

The proportion of The proportion of

The proportion of
1 in 7 births is women with diabetes women with diabetes
women with GDM is
affected by GDM first detected in detected before
85.1%
pregnancy is 7.4% pregnancy is 7.5%

GDM is the leading cause of diabetes during pregnancy

GDM: gestational diabetes mellitus.

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Complications of GDM

• Untreated GDM can affect both the mother and child1

• Macrosomia, which is common in women with GDM who are not diagnosed and
treated, affects around 15%-45% of newborns2

• Women with GDM are at an increased risk of pre-eclampsia1

• Approximately 50% of women with GDM develop type 2 diabetes within five to ten
years after delivery1

• Children born to women with GDM are at eightfold increased risk of developing type 2
diabetes in their early childhood or adolescence3

• Children born to women with GDM are at an increased risk of hypoglycaemia at birth1

Untreated GDM is associated with short- and long-term complications

GDM: gestational diabetes mellitus.

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 Diagnosis of GDM

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Universal Screening for GDM

• HAPO study involved ~25,000 pregnant women who underwent a 75-g OGTT and assessed
the perinatal outcome measures
o Risk of adverse pregnancy outcomes increased continuously with increasing maternal
glucose levels

HAPO: hyperglycaemia and adverse pregnancy outcome; OGTT: oral glucose tolerance test; GDM: gestational diabetes mellitus.

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Diagnostic Criteria for GDM

• Diagnosis of GDM should be considered if one or more of the following conditions are presented
at any time during pregnancy:

One-hour plasma glucose

Fasting plasma glucose 92-
≥180 mg/dL (10.0 mmol/L)
125 mg/dL (5.1-6.9 mmol/L)
after a 75 g oral glucose load

Two-hour plasma glucose

153-199 mg/dL (8.5-11.0
mmol/L) after a 75-g oral
glucose load

Screening of hyperglycaemia during pregnancy by an OGTT should be performed early in pregnancy

for women at high risk for diabetes and between 24th week and 28th week of pregnancy in all
women
GDM: gestational diabetes mellitus; OGTT: oral glucose tolerance test.

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Glycaemic targets for GDM

• SMBG is the primary measure used for assessing glucose levels during pregnancy1

• HbA1c should be used as the secondary measure1

• Recommended HbA1c target in pregnancy is <6%, if this can be achieved without hypoglycaemia1

One-hour Postprandial Two-hour Postprandial

Guidelines1,2 Fasting Pre-meal (mmol/L) (mmol/L)

≤95 mg/dL (5.3 mmol/L) ≤140 mg/dL (7.8 mmol/L) ≤120 mg/dL (6.7 mmol/L)
ADA -

ADA: American Diabetes Association; GDM: gestational diabetes mellitus; HbA1c: glycated haemoglobin;
SMBG: self-monitoring of blood glucose.

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Strict Glycaemic Control

4.5
4

Women with GDM (Between the 24th week

4

and the 34th week of Gestation) (%)

3.5
3
3

2.5
Intervention group
2
Standard care
1.5
1 1
1

0.5

0
**P = 0.01 Any serious peri-natal Shoulder dystocia
complications

Treating pregnant women with mild GDM is beneficial for both the women and their infants.

GDM: gestational diabetes mellitus.

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 Management of GDM

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Medical Nutrition Therapy

• MNT is the mainstay of treatment for GDM

• Diet plan is recommended to achieve
o Minimum nutrient requirements for pregnancy
o Glycaemic goals without resulting in excessive
weight gain or weight loss
• In women who are obese (BMI – 30 kg/m2) a relatively small
weight gain during pregnancy of 7 kg or 15 lb is
recommended
• In women who are underweight (BMI – 18.5 kg/m2) a
proportionally greater weight gain (up to 18 kg or 40 lb) is
recommended
• Diet plans should be individualised and culturally
appropriate
• For overweight and obese women with GDM, modest
energy and carbohydrate restriction may be appropriate
• Ketonaemia due to starvation ketosis should be avoided
• Referral to a registered dietitian or qualified person with
experience in the management of GDM
o Recommended for the best practice of MNT
BMI: Body mass index; GDM: gestational diabetes mellitus; MNT: medical nutrition therapy.

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Medical Nutrition Therapy

• Patients should be educated about

o Carbohydrate counting
o Use of food record
o Postprandial fingerstick capillary blood glucose test
• Nutrition interventions for GDM should include
o Healthy food choices
o Portion control
o Cooking practices
 Continued in the postpartum period can potentially
help to prevent
 Diabetes and its complications

GDM: gestational diabetes mellitus.

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Physical Activity

• Physical activity should be planned for 30 min/day for all women

o Walking briskly
o Doing arm exercises while seated in a chair for at least 10
minutes after each meal
• In previously sedentary individuals with GDM
o Regular aerobic exercise with proper warm-up and cool-down
steps
 Reduces fasting and postprandial glucose concentrations

GDM: gestational diabetes mellitus.

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Monitoring in Pregnancy

Foetal Monitoring
• Foetal ultrasound screening for congenital anomalies is recommended in women with GDM who
present with
o HbA1c ≥7.0% or
o Fasting plasma glucose >120 mg/dL (6.7 mmol/L)
• Use of ultrasound measurements is recommended to detect foetal macrosomia
• Based on the severity of maternal hyperglycaemia or the presence of other adverse clinical
factors, type and frequency of surveillance for foetal well-being should be considered
• Women with GDM should be educated about monitoring of foetal movements during the last eight
to ten weeks of pregnancy and to report immediately if there is any reduction in the perception of
foetal movements
Maternal Monitoring
• In women with GDM, since the risk of hypertension is high, measurement of blood pressure and
urinary protein is recommended at each prenatal visit to detect the development of pre-eclampsia

HbA1c: glycated haemoglobin; GDM: gestational diabetes mellitus.

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Pharmacological Therapy

• Approximately 70%-85% of GDM can be managed with lifestyle modifications alone1

• If treatment targets are not met, usually within one to two weeks, pharmacotherapy should be
initiated
• As per the ADA guideline, initiation of insulin therapy to be based on measures of maternal
glycaemia with or without assessment of foetal growth characteristics
• ACOG guideline advocates that insulin therapy should be initiated based on the measures of
maternal glycaemia, further based on fasting, one-hour and two-hour plasma glucose levels
• Glyburide and metformin are considered safe and effective; however, long-term safety data are
inadequate

ADA: American Diabetes Association; ACOG: American College of Obstetricians and Gynecologists; GDM: gestational diabetes mellitus.

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Insulin Therapy

• With the available efficacy and safety evidence with the various
insulin products, it is reasonable to utilise any of the insulin
products (regular, NPH, or one of the analogs) in the
management of GDM1
• Providers can select a product and delivery form (pen or vial and
syringe) based on the patient’s needs2
• Constant insulin adjustment is necessary to keep up with the
increasing insulin requirement of pregnancy2
• If treatment is required, the safety of agents in breastfeeding must
be considered2

GDM: gestational diabetes mellitus; NPH: neutral protamine Hagedorn.

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Metformin

• Metformin can cross the placenta1

• Used in women with polycystic ovarian syndrome to improve fertility and decrease the
spontaneous abortion rate1
• In the MiG trial, 751 women with GDM randomly assigned to open treatment with metformin (with
supplemental insulin if required) or insulin at 20-33 weeks of gestation demonstrated2
o Metformin (alone or with supplemental insulin) is not associated with increased perinatal
complications compared with insulin
o In addition, women preferred metformin to insulin treatment
• In the MiG TOFU trial, children born to women with GDM, who were exposed to metformin in
utero, had larger subscapular and biceps skinfolds, however they did not show any difference in
total or percentage body fat compared with children whose mothers were treated during pregnancy
with insulin alone3

GDM: gestational diabetes mellitus; MiG: Metformin in Gestational diabetes; TOFU: The Offspring Follow-Up.

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Glyburide

• Glyburide is shown to have minimal transfer across the human placenta (4% ex vivo) and has not
been associated with excess neonatal hypoglycaemia
• Glyburide is a useful adjunct to MNT/physical activity regimens when additional therapy is needed
to maintain target glucose levels
• Glyburide action must be carefully balanced with meals and snacks to prevent maternal
hypoglycaemia
• As with MNT/physical activity and insulin regimens, SMBG and foetal measurements of abdominal
circumference or other parameters of foetal size need to be followed closely in women using
glyburide

MNT: medical nutrition therapy; SMBG: self-monitoring blood glucose.

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Tests Recommended Post-Delivery

Tests Recommended Following GDM

GDM: gestational diabetes mellitus; OGTT: oral glucose tolerance test.

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 Prevention of Diabetes

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Diabetes Prevention

• While diagnosing GDM, women at high risk for diabetes are identified; therefore, it is important to
educate the patient about the need for primary diabetes prevention
• Lifestyle change and use of metformin or thiazolidinediones (pioglitazone) can prevent or delay the
progression of impaired glucose tolerance (IGT) to type 2 diabetes after GDM
• Risks for the development of CVD need to be established by follow-up studies in women with
previous GDM
• Researchers and healthcare providers should actively support public health initiatives to educate
public, patients and providers about the risk of GDM

CVD: cardiovascular disease; IGT: impaired glucose tolerance; GDM: gestational diabetes mellitus.

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Pregnancy Planning

• Pregnancy planning should include

 Evaluation of glucose tolerance and, if abnormal,
 Hyperglycaemia should be treated before the
discontinuation of contraception
• Oral contraceptives of lowest doses should be prescribed
and can be initiated six to eight weeks after delivery if the
woman is breastfeeding
• However, progestin-only agents should be used with caution
during breastfeeding.

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Summary

• GDM, the leading cause of diabetes in pregnancy, affects approximately 21 million

live births
• Untreated GDM is associated with short- and long-term complications
• Both mother and child are at risk of type 2 diabetes mellitus as a long-term
complication
• Based on the HAPO study results, universal screening for GDM at 24-28 weeks of
gestation is recommended
• Maintaining optimised glycaemic control can reduce perinatal complications
• Majority of GDM can be managed by lifestyle modifications alone
• If treatment targets are not met with lifestyle modification, pharmacotherapy should
be initiated
• As the diagnosis of GDM identifies women at high risk for diabetes, it is important to
educate the patient about the need for primary diabetes prevention

GDM: gestational diabetes mellitus; HAPO: hyperglycaemia and adverse pregnancy outcome.

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