Primary prevention
There is some evidence that dietary measures taken prior to pregnancy may reduce the risk of GDM. Although there are no strong conclusions as to the best pre-conception intervention for the prevention of GDM, some evidence suggests that a Mediterranean diet may lower the risk of developing GDM.[28]
As GDM recurs in 30% to 84% of subsequent pregnancies, it is appropriate to inform women with previous GDM that it may recur.[4][17] Although advising patients with a history of GDM to take steps to minimise their risk of recurrence through pre-pregnancy changes to diet and exercise may appear rational, the evidence to support this remains uncertain.[29]
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One systematic review and meta-analysis of observational studies reporting the association between interpregnancy weight change and GDM noted that, in those with a BMI >25 kg/m², the risk of GDM in subsequent pregnancies decreases with interpregnancy weight loss.[30]
Once a woman is pregnant, it is reasonable to recommend a healthy diet, weight gain within the Institute of Medicine guidelines, and physical activity.[31][32]
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Evidence on whether this reduces the risk of GDM remains unclear and further high-quality evidence is needed. One randomised study in Finland demonstrated a significant (39%) decrease in the incidence of GDM in high-risk women who received a lifestyle intervention that combined dietary counselling, physical activity, and limitation of weight gain, as compared with the control group.[33] One systematic review of combined diet and exercise interventions during pregnancy suggests that they may be effective at reducing the risk of GDM, as well as reducing gestational weight gain, compared with standard care.[34][35]
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However, one meta-analysis of interventions aiming to prevent the development of GDM in women with overweight or obesity showed no benefit of interventions (i.e., diet, exercise, or combination) in preventing GDM when applied during pregnancy.[36]
In pregnant women with overweight and obesity, there is evidence to suggest that the amount of maternal weight gain during pregnancy may be reduced by multi-disciplinary antenatal care (including continuity of obstetric provider; regular weigh-ins; brief intervention by a dietitian to ask about eating habits and provide advice on healthy eating; and clinical psychology management to assess for psychological factors involved in eating patterns, symptoms of depression/anxiety, and presence of stressful life events) and general antenatal dietary and lifestyle interventions.[37] Two randomised controlled trials have now found that starting metformin in the second trimester did not reduce the risk of GDM in women with overweight or obesity.[38][39]
Secondary prevention
Women diagnosed with GDM are over 20 times more likely to go on to develop type 2 diabetes than the general population.[96] A European Society of Cardiology report highlighted that:[97]
An estimated 10% of women with GDM will have diabetes mellitus diagnosed soon after delivery with at least another 20% affected by impaired glucose metabolism at postnatal screening.
Of the remaining women, 20% to 60% will develop type 2 diabetes mellitus later in life, often within 5 to 10 years after the index pregnancy. The risk is greatest in the first year following delivery but persists for 25 years.[98]
Support women who have a history of GDM to make lifestyle changes to reduce the risk of type 2 diabetes and cardiovascular disease.
In particular, women whose postnatal tests show impaired fasting glucose (between 6.0 mmol/L and 6.9 mmol/L [108-124 mg/dL]) or impaired glucose tolerance should start an exercise programme and change diet to reduce their risk of developing type 2 diabetes.[3][4]
One systematic review and meta-analysis noted that development of type 2 diabetes is 18% higher per unit of BMI increase from pre-pregnancy BMI at follow-up, highlighting the importance of effective weight management after GDM.[3][114] Another systematic review and meta-analysis of randomised controlled trials suggests that post-delivery lifestyle interventions in patients with prior GDM are effective in reducing the risk of type 2 diabetes.[3][115]
Breastfeeding may be beneficial for women who have had GDM. There are limited data to suggest that lactation is associated with an improvement in fasting and post-prandial hyperglycaemia in women with recent GDM.[116] Population-based data also suggest that a greater length of lifetime lactation is associated with a lower risk for type 2 diabetes.[117] The American Diabetes Association (ADA) recommends that breastfeeding should be considered in order to reduce the risk of maternal type 2 diabetes.[3]
In the UK, the National Institute for Health and Care Excellence recommends an annual HbA1c test for any woman with a history of gestational diabetes who had a negative postnatal test for diabetes.[4] In practice these appointments can easily be missed in the UK as they fall between primary and secondary care teams.[96] GPs can:
Encourage attendance and follow-up with patients who miss appointments
Refer women who were diagnosed with GDM to the NHS Diabetes Prevention Programme.
GDM is associated with a twofold increased risk of future cardiovascular events, with the risk being apparent within 10 years after pregnancy.[97] In the long-term, therapeutic lifestyle changes such as diet, exercise, and smoking cessation are important to reduce the risk of cardiovascular disease.[118] Offer all women lifestyle advice, including advice on weight control, diet, and exercise.
The ADA notes that pharmacotherapy (e.g., for weight management, minimising the progression of hyperglycaemia, or cardiovascular risk reduction), may be considered as a preventative measure in people at high risk of developing type 2 diabetes, including those with a history of GDM.[3]
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