Key messages

  • Glucose tolerance abnormalities have immediate, short and long term health implications for women and babies.
  • All women should be offered an oral glucose tolerance test (OGTT).
  • The risk of adverse pregnancy outcomes increases with rising maternal glucose levels.
  • Women should be given dietary and exercise advice to help them control their blood sugars and achieve appropriate gestational weight gain.

Quick Links

Clinician information

  • GDM screening flowchart
  • Hypoglycaemia management flowchart

Patient information

Gestational diabetes

  • Gestational diabetes mellitus (GDM) is defined as any degree of glucose intolerance with the onset or first recognition during pregnancy.
  • GDM is associated with significant morbidity: a diagnosis of GDM has immediate, short and long term health implications for women and babies.
  • GDM usually resolves following birth. 
  • There is a clear relationship between increased plasma glucose levels during pregnancy and adverse fetal and maternal outcomes, independent of other known factors for these outcomes.

Care of women with an existing diagnosis of type 1 or type 2 diabetes, women undertaking continuous glucose monitoring, and women found to have pre-existing (overt) diabetes is beyond the scope of this guidance.

Risks associated with GDM

Table 1. Risks associated with GDM

Maternal short term Maternal long term Newborn/fetal short term Newborn long term
  • Pre-eclampsia
  • Polyhydramnios
  • Induced labour
  • Operative birth
  • Postpartum haemorrhage
  • Infection
  • Recurrent GDM
  • Progression to type 2 diabetes
  • About 5% develop type 2 diabetes within 6 months of birth
  • About 60% develop type 2 diabetes within 10 years
  • Development of cardiovascular disease
  • Congenital abnormalities
  • Respiratory distress syndrome
  • Jaundice
  • Hypoglycaemia
  • Premature birth
  • Hypocalcaemia
  • Polycythaemia
  • Increased newborn weight and adiposity
  • Macrosomia
  • Shoulder dystocia - risk increases as fetal weight increases
  • Bone fracture
  • Nerve palsy
  • Caesarean section birth
  • Hypoxic-ischaemic encephalopathy (HIE)
  • Death
  • Impaired glucose tolerance
  • Development of type 2 diabetes
  • Obesity

Screening and diagnosis

Screening

GDM screening flowchart

  • Screen all women for risk factors (Table 2) at booking.
  • Perform a random blood glucose level (RBGL) on all women at booking; ensure that they have not been fasting. 
  • Refer all women with risk factors and/or a RBGL >11.0 mmol/L for an oral glucose tolerance test (OGTT) at 14-16 weeks:
    • normal result = repeat OGTT at 26-28 weeks
    • abnormal result = diabetes care.
  • Refer all women with no risk factors or a normal first trimester OGTT for an OGTT at 26-28 weeks:
    • normal result = routine antenatal care
    • abnormal result = diabetes care.

Table 2. Risk factors for GDM

Booking BMI >30 Previous GDM
Age ≥40 years Previous elevated BGL
Ethnicity (Asian, Indian subcontinent, Aboriginal, Torres Strait Islander, Pacific Islander, Maori, Middle Eastern, non-white African) Family history of diabetes (first degree relative, or sister with GDM)
Previous macrosomic baby (birth weight >4500 g or >90th centile) Previous perinatal loss
Polycystic ovarian syndrome (PCOS) Medications (corticosteroids, antipsychotics)
Multiple pregnancy

Diagnosis

  • Diagnosis of GDM is based on results of the fasting 75 g OGTT.
  • One elevated plasma glucose level is sufficient for a diagnosis (see Table 3).
  • If a fasting glucose test has been performed for other reasons and shows an elevated value, this may be accepted as diagnostic of GDM.
  • HbA1c of 41–48 mmol/mol (5.9–6.5%) in early pregnancy may be sufficient to diagnose pre-existing (overt) diabetes and requires review by an endocrinologist.
  • Type 1 diabetes can present in pregnancy.

Table 3. Criteria for diagnosis of GDM

Time Plasma glucose
Fasting 5.1–6.9 mmol/L
1 hour ≥10.0 mmol/L
2 hour 8.5–11.0 mmol/L

Table 4. Criteria for diagnosis of pre-existing (overt) diabetes

Time Plasma glucose
Fasting ≥7.0 mmol/L
1 hour -
2 hour ≥11.1 mmol/L

Care of women with an existing diagnosis of type 1 or type 2 diabetes, women undertaking continuous glucose monitoring, and women found to have pre-existing (overt) diabetes is beyond the scope of this guidance.

Optimal management

Antenatal care

  • Objectives for antenatal care are:
    • effective control of blood glucose level (BGL)
    • monitoring for maternal complications 
    • preventing fetal/neonatal complications.
  • Provide women with information about gestational diabetes (patient resources).

Table 5. Management of diet-controlled GDM

Antenatal care

Consider low risk model with shared midwifery and medical care.
Collaborate with the diabetes team.

Diabetes educator Refer for review at diagnosis, then 1–4 weekly.
Dietitian Refer for review at diagnosis, then as required.
Endocrinologist / obstetric physician Refer for review if glycaemic control is suboptimal.
CTG monitoring Offer from ≥38/40.
May be required earlier if other risk factors are identified (such as abnormal fetal growth, hypertensive disorders).
Ultrasound surveillance Consider 4–6 weekly in the 3rd trimester for women with suboptimal glycaemic control.
Corticosteroid administration Consult endocrinologist / obstetric physician.
Consider admission to hospital for inpatient monitoring.
Consider insulin treatment for 48 hours, especially if the woman demonstrates hyperglycaemia after the first dose.
Anaesthetic review Refer women with comorbidities (such as obesity, autonomic neuropathy) for review in the 3rd trimester.
Lactation support Women at low risk of complications may choose to express and store breast milk from 36 weeks gestation to support timely infant feeding.
Timing of birth Elective delivery is not required for GDM as an isolated risk factor, with optimal glycaemic control.
If glycaemic control is suboptimal, plan for care based on the woman's individual clinical presentation
Postpartum care Recommend and support breastfeeding.
Ensure any expressed colostrum accompanies the mother and is readily available for use if required.
Encourage rooming in, unless medically indicated.
Order OGTT at the six-week review.

Table 6. Management of GDM requiring medication

Antenatal care High-risk or obstetric-led model of care
Diabetes educator Refer for review at diagnosis, then 1–4 weekly
Dietitian Refer for review at diagnosis, then as required
Endocrinologist / Obstetric physician Review at commencement of pharmacotherapy, then 1–4 weekly
CTG monitoring May be required if risk factors are identified (such as abnormal fetal growth, hypertensive disorders, suboptimal glycaemic control)
Ultrasound surveillance 4–6 weekly in the 3rd trimester
Corticosteroid administration

Consider admission to hospital for inpatient monitoring
On insulin:

  • consult endocrinologist / obstetric physician for plan, including optimising insulin dosage
  • continue BGL as per current regime

On oral hypoglycaemics (OHG):

  • consult endocrinologist / obstetric physician for plan
  • continue BGL as per current regime
  • consider treatment with insulin for 48 hours, especially if woman demonstrates hyperglycaemia after the first dose of corticosteroids
Anaesthetic review Refer women with comorbidities (such as obesity, autonomic neuropathy) for review in the 3rd trimester
Lactation support Women at low risk of complications may choose to express and store breast milk from 36 weeks gestation to support timely infant feeding
Timing of birth

Timing of birth will depend on individual glycaemic control and other medical and obstetric complications.

Consider delivery from 38 weeks.

Postpartum care

Target BGL ≤11.1 mmol/L.
Cease all insulin immediately following birth.
Preprandial BGL TDS and BGL before bed.
If fasting BGL is >7.0, contact the appropriate medical officer.
Recommend and support breastfeeding.
Encourage rooming in, unless medically indicated.
Order OGTT at the six-week review.

Suboptimal glycaemic control

  • Suboptimal glycaemic control refers to:
    • three or more fasting BGLs ≥5.0 mmol/L in the preceding week

    or

    • three or more two-hour postprandial BGLs ≥6.7 mmol/L in the preceding week.
  • Risk factors for suboptimal glycaemic control include:
    • inconsistent blood glucose monitoring
    • inconsistent antenatal care attendance
    • possible poor compliance with blood glucose monitoring.
  • Do not rely solely on CTG for surveillance of women with suboptimal glycaemic control.

Hypoglycaemia

Diagnosis and management for women with GDM on insulin

Diagnosis

  • Symptoms of hypoglycaemia (see Table 7)
  • BGL <4.0 mmol/L

Table 7. Symptoms of hypoglycaemia

Hunger Tingling lips and/or fingers
Palpitations Blurred vision
Dizziness Confusion
Sweating Lack of concentration
Headache Behaviour changes
Irritability Lack of consciousness

Management

  • Hypoglycaemia management flowchart

Table 8. Fast and slow acting carbohydrates

Fast-acting carbohydrate – 15 g Slow-acting carbohydrate – 15 g
6–7 jellybeans 250 ml milk
½ can regular soft drink (not ?diet?) 200 g tub of yoghurt
½ glass fruit juice 1 slice of bread
3 teaspoons of sugar 2 sweet plain biscuits
3 teaspoons of honey 1 piece of fruit
Glucose tablets equivalent to 15gms Next meal (if served within 30 minutes)

Hyperglycaemia

Diagnosis and management for women with GDM on insulin

Diagnosis

  • BGL >7.0 mmol/L

Management

  • Escalate care to a senior obstetric clinician.
  • Repeat BGL in one hour.
  • Review clinical circumstances such as stage of labour and oral intake.
  • If blood glucose is not maintained between 4.0 and 7.0 mmol/L, consider subcutaneous insulin on a sliding scale (Tables 11 and 12).
  • If blood glucose is poorly controlled on a sliding scale of subcutaneous insulin, consider an insulin infusion (Table 13):
    • 50 units of Novorapid in 50 ml of 0.9% NaCl (1 unit/ml), administered via a syringe driver
    • commence rate at 1–2 ml/hr, depending on initial BGL.

Intrapartum care

Practice points

  • Target BGL is 4.0–7.0 mmol/L.
  • Blood glucose monitoring regime will depend on whether the woman has required insulin and/or OHG.
  • Use your hospital guidelines for general care during labour.
  • Order meals appropriate for a diabetic diet.
  • If a woman has an elective or emergency caesarean under general anaesthetic, monitor her BGL every 30 minutes from induction of anaesthesia until full consciousness is regained.
  • Ensure any expressed colostrum accompanies the mother and is readily available for use if required.

Table 9. Spontaneous or induced labour – management and monitoring

Intrapartum management BGL monitoring Fetal monitoring
Diet control Standard care 4-hourly Consider continuous CTG where other complications are present See - RANZCOG Intrapartum Fetal Surveillance Algorithm
Insulin

Spontaneous labour:

  • cease insulin when labour established

Morning IOL (labour not established):

  • eat breakfast
  • give usual rapid-acting insulin
  • omit morning dose of long or intermediate acting insulin

Afternoon IOL (labour not established):

  • give usual mealtime insulin
  • give usual bedtime insulin
2-hourly Continuous CTG
OHG Cease OHG when labour established 2-hourly Continuous CTG

Table 10. Elective caesarean  – management and monitoring

Intrapartum management BGL monitoring
Diet control Standard care None required during caesarean section (CS)
Insulin Give usual insulin the night before CS Fast as per hospital instructions Fasting BGL before attending hospital Monitor BGL 2-hourly
OHG Cease OHG 24 hours prior to CS Fast as per hospital instructions Fasting BGL before attending hospital Monitor BGL 2-hourly

Intrapartum insulin treatment

Table 11. Insulin sliding scale: women receiving <40 units insulin/day

BGL mmol/L Action
0­–6 No insulin
6.1–8.0 2 units rapid-acting insulin (e.g. Novorapid, Humalog)
8.1–10 4 units rapid-acting insulin
10.1–14 6 units rapid-acting insulin
>14 8 units and medical review

Table 12. Insulin sliding scale: women receiving ≥40 units insulin/day

BGL mmol/L Action
0–6 No insulin
6.1–8.0 4 units rapid-acting insulin
8.1–10 6 units rapid-acting insulin
10.1–14 8 units rapid-acting insulin
>14 10 units and medical review

Table 13. Insulin infusion – Novorapid in 0.9% NaCl (1 unit/ml) 

BGL mmol/L Infusion rate
Starting rate 1–2 ml/hr, depending on initial BGL
<4.0 Decrease rate by 1 ml/hr
Give 15 grams of fast acting carbohydrate 
4.0–7.0 Maintain at 1–2 ml/hrc
>7.0 Increase rate by 1 ml/hr

Postnatal care

Care of the woman

  • Target BGL ≤ 11.1 mmol/L.
  • Cease all insulin immediately following birth.
  • Monitor BGL (see Table 14).
  • Recommend and support breastfeeding.
  • Send the placenta for pathological examination and follow up results.

Table 14. Postpartum BGL monitoring in hospital


Postpartum monitoring Required intervention
Diet controlled Not required Order OGTT at the six-week review
Insulin/OHG requiring  Preprandial BGL QID
BGL before bed
If fasting BGL is >7.0, contact the appropriate Medical Officer
Order OGTT at the six-week review

Care of the baby

Follow-up

Practice points

  • Discuss with the woman and provide a referral for:
    • OGTT at 6–12 weeks post birth
    • dietitian follow-up. 
  • Advise the woman to make an appointment to see her GP six weeks post birth.
  • Notify the GP of the woman’s diagnosis, management and any associated outcomes.
  • Women eligible for Medicare are automatically registered on the National Gestational Diabetes Register via the National Diabetes Services Scheme (NDSS) and they and their GPs are sent a six-week and subsequent annual reminder. Woman can opt out via the NDSS website.
  • Long-term follow-up includes:
    • annual HbA1c
    • HbA1C prior to pregnancy where possible
    • OGTT in first trimester of subsequent pregnancy, with repeat OGTT at 28/40 if first is NAD.

More information

Audit and performance improvement

All maternity services should have processes in place for: 

  • auditing clinical practice and outcomes
  • providing feedback to clinicians on audit results
  • addressing risks, if identified
  • implementing change, if indicated.

Potential auditable standards include:

  • number of women with identified risk factors who have an early OGTT
  • number of newborns who require SCN or NICU admission
  • number of newborns exclusively breastfeeding at discharge to home.

For further information or assistance with auditing, please contact the Maternity and Newborn Clinical Network: maternityehandbook@safercare.vic.gov.au

References

  • Australian Commission on Safety and Quality in Healthcare. National consensus statement: essential elements for recognising and responding to clinical deterioration. 2010 [cited 2014, May 14]. 
  • Australian Health Ministers’ Advisory Council. Clinical practice guidelines: antenatal care - module II. Australian Government Department of Health, Canberra 2014.
  • Australian Institute of Health and Welfare. Diabetes in pregnancy: its impact on Australian women and their babies. Diabetes series no.14. Cat.no. CVD 52. Canberra. 2010 [cited 2014 December 05].
  • Blumer I, Hadar E, Hadden DR, Jovanovic L, Mestman JH, Hassan Murad M, et al. Diabetes and pregnancy: an Endocrine Society clinical practice guideline. Journal of Clinical Endocrinology & Metabolism. 2013; 98:4227-49. 
  • Clinical Guidelines, Obstetric and Midwifery. Diabetes In pregnancy: management of gestational diabetes In The Team Obstetric Clinics. Women and Newborn Health Service, King Edward Memorial Hospital. Western Australia Department of Health. 2015. 
  • Diabetes Australia Ltd. The National Diabetes Service Scheme (NDSS). 2015 [cited 2015 January 05]. 
  • Diabetes mellitus: management of gestational diabetes guideline. The Royal Women’s Hospital. Melbourne Victoria.  2015.
  • Falavigna M, Schmidt MI, Trujillo J, Alves LF, Wendland ER, Torloni MR, et al. Effectiveness of gestational diabetes treatment: a systematic review with quality of evidence assessment. Diabetes Res Clin Pract. 2012; 98(3):396-405. 
  • Forster, D. et.al. (2017) Advising women with diabetes in pregnancy to express breastmilk in late pregnancy (Diabetes and Antenatal Milk Expressing [DAME]): a multicentre, unblinded, randomised controlled trial. The Lancet 389 (10085), 2204-2213. DOI: 10.1016/S0140-6736(17)31373-9 
  • Hartling L, Dryden DM, Guthrie A, Muise M, Vandermeer B & Donovan L. Benefits and harms of treating gestational diabetes mellitus: a systematic review and meta-analysis for the U.S. Preventive Services Task Force and the National Institutes of Health Office of Medical Applications of Research. Ann Intern Med. 2013; 159(2):123-9.
  • Maternity and Neonatal Clinical Guideline. Queensland clinical guideline: gestational diabetes mellitus, Queensland Health. Queensland. 2015.
  • Nankervis A, McIntyre H, Moses R, Ross G, Callaway L, Porter C, et al. ADIPS consensus guidelines for the testing and diagnosis of gestational diabetes mellitus in Australia and New Zealand. 2014. 
  • NSW Health. Maternity – SESLHD gestational diabetes mellitus management (gdm) policy. Maternity Guideline. NSW Health. Government of NSW, 2014. 
  • Royal Australian and New Zealand College of Obstetricians and Gynaecologists. Diagnosis of gestational diabetes mellitus (GDM) and diabetes mellitus in pregnancy. C-Obs 7. 2015.
  • Royal Hospital for Women (2013) Diabetes mellitus – management in pregnancy. Retrieved from http://www.seslhd.health.nsw.gov.au/rhw/manuals/documents/Diabetes/Diabetes Mellitus - Management in Pregnancy.pdf [no longer exists]
  • SA Health (2015) Insulin infusion regimen clinical guideline.
  • South Australian Perinatal Practice Guidelines, Diabetes mellitus and gestational diabetes. SA Maternal & Neonatal Clinical Network: SA Health, Government of South Australia, 2015.
  • The Royal Women’s Hospital (2017) Diabetes in pregnancy: management in labour.
  • Tieu J, McPhee A, Crowther C, Middleton P. Screening and subsequent management for gestational diabetes for improving maternal and infant health. Cochrane Database of Systematic Reviews 2014, Issue 2. Art. No.: CD007222. DOI: 10.1002/14651858.CD007222.pub3. 2014. 
  • World Health Organization. Diagnostic criteria and classification of hyperglycaemia first detected in pregnancy. 2013.

Abbreviations

AC Abdominal circumference
BGL Blood glucose level
BMI Body mass index
BGL Blood glucose level
CS Caesarean section
GDM Gestational diabetes mellitus
HbA1C Haemoglobin A1c
IOL Induction of labour
LGA Large for gestational age
MNT Medical nutrition therapy
NDSS National Diabetes Services Scheme
OHG Oral hypoglycaemic medication
OGTT Oral glucose tolerance test – 75 gram glucose load
US Ultrasound scan