management of gestational diabetes

Last reviewed 09/2022

Seek specialist advice.

The main themes of diabetic management in pregnancy is the maintenance of good control of the diabetes, and regular ultrasound examination of the foetus.

The management of the pregnant diabetic is best undertaken using a team approach. Some general principles concerning the management of a diabetic patient are outlined below:

• health care team - members include:
• obstetrician
• midwife
• physician
• general practitioner

A summary of the NICE guidance regarding management gestational diabetes (1) is included below.

NICE suggest testing criteria for gestational diabetes as:

• do not use fasting plasma glucose, random blood glucose, HbA1c, glucose challenge test or urinalysis for glucose to assess risk of developing gestational diabetes
  
  
• use the 2-hour 75 g oral glucose tolerance test (OGTT) to test for gestational diabetes in women with risk factors (see below)
  
  
• offer women who have had gestational diabetes in a previous pregnancy:
  • early self-monitoring of blood glucose or
  • a 75 g 2-hour OGTT as soon as possible after booking (whether in the first or second trimester), and a further 75 g 2-hour OGTT at 24-28 weeks if the results of the first OGTT are normal
    
    
• offer women with any of the other risk factors for gestational diabetes a 75 g 2-hour OGTT at 24-28 weeks (see below)
  
  

• glycosuria detected by routine antenatal testing

  • be aware that glycosuria of 2+ or above on 1 occasion or of 1+ or above on 2 or more occasions detected by reagent strip testing during routine antenatal care may indicate undiagnosed gestational diabetes. If this is observed, consider further testing to exclude gestational diabetes

• risk factors for gestational diabetes:
  • BMI above 30 kg/m2
  • previous macrosomic baby weighing 4.5 kg or above
  • previous gestational diabetes
  • family history of diabetes (first-degree relative with diabetes)
  • minority ethnic family origin with a high prevalence of diabetes
    
    
• diagnosis of gestational diabetes
  • diagnose gestational diabetes if the woman has either:
    
    
    • a fasting plasma glucose level of 5.6mmol/litre or above or
      
      
    • a 2-hour plasma glucose level of 7.8mmol/litre or above

Interventions

• offer a trial of changes in diet and exercise to women with gestational diabetes who have a fasting plasma glucose level below 7 mmol/L at diagnosis
  
  
• women with gestational diabetes should be advised to take regular exercise (such as walking for 30minutes after a meal) to improve blood glucose control
  
  
• offer metformin to women with gestational diabetes if blood glucose targets are not met using changes in diet and exercise within 1-2 weeks
  
  
• offer insulin instead of metformin to women with gestational diabetes if metformin is contra-indicated or unacceptable to the woman
  
  
• offer addition of insulin to the treatments of changes in diet, exercise and metformin for women with gestational diabetes if blood glucose targets are not met
  
  
• offer immediate treatment with insulin, with or without metformin, as well as changes in diet and exercise, to women with gestational diabetes who have a fasting plasma glucose level of 7.0 mmol/L or above at diagnosis
  
  
• consider immediate treatment with insulin, with or without metformin, as well as changes in diet and exercise, for women with gestational diabetes who have a fasting plasma glucose level of between 6.0 and 6.9 mmol/L if there are complications such as macrosomia or hydramnios
  
  
• consider glibenclamide for women with gestational diabetes in whom blood glucose targets are not achieved with metformin but who decline insulin therapy, or who cannot tolerate metformin

Target blood glucose levels

• advise pregnant women with any form of diabetes to maintain their capillary plasma glucose below the following target levels, if these are achievable without causing problematic hypoglycaemia:
  • fasting: 5.3 mmol/litre and
    
    
  • 1 hour after meals: 7.8mmol/litre or 2 hours after meals: 6.4mmol/litre
    
    
• if on insulin or glibenclamide then advise the women to maintain their capillary plasma glucose level above 4mmol/litre

Renal assessment during pregnancy

• if renal assessment has not been undertaken in the preceding 3 months in women with pre-existing diabetes, arrange it at the first contact in pregnancy. If the serum creatinine is abnormal (120 micromol/litre or more), the urinary albumin:creatinine ratio is greater than 30 mg/mmol or total protein excretion exceeds 2 g/day, referral to a nephrologist should be considered (eGFR should not be used during pregnancy). Thromboprophylaxis should be considered for women with proteinuria above 5 g/day (macroalbuminuria)

Ketone testing and diabetic ketoacidosis

• advise pregnant women with type 2 diabetes or gestational diabetes to seek urgent medical advice if they become hyperglycaemic or unwell
• test urgently for ketonaemia if a pregnant woman with any form of diabetes presents with hyperglycaemia or is unwell, to exclude diabetic ketoacidosis

Monitoring HbA1c

• measure HbA1c levels in all women with gestational diabetes at the time of diagnosis to identify those who may have pre-existing type 2 diabetes
• no role for HbA1c for monitoring in gestational diabetes

Screening for congenital malformations

• women with diabetes should be offered an ultrasound scan for detecting fetal structural abnormalities, including examination of the fetal heart (4 chambers, outflow tracts and 3 vessels), at 20 weeks

Monitoring fetal growth and well-being

• pregnant women with diabetes should be offered ultrasound monitoring of fetal growth and amniotic fluid volume every 4 weeks from 28 to 36 weeks
• routine monitoring of fetal well-being before 38 weeks is not recommended in pregnant women with diabetes, unless there is a risk of intrauterine growth restriction
• women with diabetes and a risk of intrauterine growth restriction (macrovascular disease and/or nephropathy) will require an individualised approach to monitoring fetal growth and well-being

Preterm labour in women with diabetes

• diabetes should not be considered a contraindication to antenatal steroids for fetal lung maturation or to tocolysis
• women with insulin-treated diabetes who are receiving steroids for fetal lung maturation should have additional insulin according to an agreed protocol and should be closely monitored
• beta-mimetic drugs should not be used for tocolysis in women with diabetes

Timing and mode of birth

• advise women with gestational diabetes to give birth no later than 40+6 weeks, and offer elective birth (by induction of labour, or by caesarean section if indicated) to women who have not given birth by this time
• consider elective birth before 40+6 weeks for women with gestational diabetes if there are maternal or fetal complications.

Blood glucose control during labour and birth

• monitor capillary plasma glucose every hour during labour and birth in women with diabetes, and ensure that it is maintained between 4 and 7 mmol/litre

Notes:

• NICE state with respect to the use of metformin and glibenclamide in pregnancy (2):
  • metformin is used in UK clinical practice in the management of diabetes in pregnancy and lactation. There is strong evidence for its effectiveness and safety, which is presented in the full version of the guideline. This evidence is not currently reflected in the SPC (February 2015). The SPC advises that when a patient plans to become pregnant and during pregnancy, diabetes should not be treated with metformin but insulin should be used to maintain blood glucose levels. Informed consent on the use of metformin in these situations should be obtained and documented
  • at the time of publication (February 2015) glibenclamide was contraindicated for use up to gestational week 11 and did not have UK marketing authorisation for use during the second and third trimesters of pregnancy in women with gestational diabetes. The prescriber should follow relevant professional guidance, taking full responsibility for the decision. Informed consent should be obtained and documented

Reference:

• (1) Diabetes UK. Recommendations for the management of pregnant women with diabetes (including gestational diabetes). 2003
• (2) NICE (February 2015). Diabetes in pregnancy Management of diabetes and its complications from pre-conception to the postnatal period