Primary prevention
There is some evidence that dietary measures taken prior to pregnancy may reduce the risk of gestational diabetes mellitus (GDM). Although there are no strong conclusions as to the best pre-conception intervention, some evidence suggests that a Mediterranean diet may lower the risk of developing GDM.[33]
Once a woman is pregnant, it is reasonable to recommend a healthy diet, weight gain within the Institute of Medicine guidelines, and physical activity.[21][34]
[ 
]
Evidence on whether this reduces the risk of GDM remains unclear, however, 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, compared with the control group.[35] One systematic review found that combined diet and exercise interventions during pregnancy may be effective at reducing the risk of GDM and reducing gestational weight gain compared with standard care, but the authors concluded that further high-quality evidence is needed.[36][37]
[ ]
[ ]
Meanwhile, one meta-analysis of interventions aiming to prevent the development of GDM in women with overweight or obesity showed no benefit of interventions (diet, exercise, or combination) in preventing GDM when applied during pregnancy.[38]
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.[39] Two randomised controlled trials have now found that starting metformin in the second trimester does not reduce the risk of GDM in women with overweight or obesity.[40][41]
Secondary prevention
Prevention of recurrent GDM
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 seems rational, the evidence to support this remains uncertain.[141]
[ ]
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 decreased with interpregnancy weight loss.[142]
Prevention of type 2 diabetes
Women diagnosed with GDM are over 20 times more likely to go on to develop type 2 diabetes than the general population.[138] A European Society of Cardiology report highlighted that an estimated 10% of women with GDM will be diagnosed with diabetes mellitus soon after delivery, with at least another 20% found to have impaired glucose metabolism at postnatal screening.[117] Of the remaining women, 20% to 60% will develop type 2 diabetes mellitus later in life, often within 5-10 years of the index pregnancy. The risk is greatest in the first year following delivery, but persists for 25 years.[118]
In the UK, the National Institute for Health and Care Excellence (NICE) recommends an annual haemoglobin A1c (HbA1c) test for any woman with a history of GDM who had a negative postnatal test for diabetes.[4]
In practice, these appointments can easily be missed as they fall between primary and secondary care teams.[138] To optimise engagement, general practitioners (GPs) are advised to encourage attendance, follow-up with patients who miss appointments, and refer women who were diagnosed with GDM to the NHS Diabetes Prevention Programme.[4][137]
Support women who have a history of GDM to make lifestyle changes to reduce the risk of type 2 diabetes.
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 their diet to reduce the risk of developing type 2 diabetes.[3][4]
One systematic review and meta-analysis found that the risk of developing type 2 diabetes increases by 18% for each unit rise in BMI from the pre-pregnancy level at follow-up, underscoring the importance of effective weight management after GDM.[143] Another systematic review and meta-analysis suggested that post-delivery lifestyle interventions in patients with prior GDM can effectively reduce the risk of type 2 diabetes.[144] In a large prospective cohort study of high risk women with a history of GDM who were followed up for 28 years, maintaining optimal levels of five modifiable risk factors (BMI <25 kg/m², high-quality diet, moderate alcohol consumption [5.0-14.9 g/day], regular exercise [≥150 minutes/week of moderate intensity or ≥75 min/week of vigorous intensity] and no current smoking) was associated with a more than 90% relative reduction in the risk of incident type 2 diabetes after adjustment for other major diabetes risk factors.[145] These benefits were consistently observed even among women with overweight or obesity and those with higher genetic susceptibility to type 2 diabetes.
Breastfeeding may be beneficial for women who have had GDM and is recommended by the American Diabetes Association and American Heart Association (AHA) to reduce the risk of subsequent type 2 diabetes.[3][115]
There are limited data to suggest that lactation is associated with an improvement in fasting and post-prandial hyperglycaemia in women with recent GDM.[146] Population-based data suggest that a greater length of lifetime lactation is associated with a lower risk for type 2 diabetes.[147]
Prevention of cardiovascular disease
GDM is associated with a twofold increased risk of future cardiovascular events, with the risk being apparent within 10 years after pregnancy.[117] This increased risk is independent of the development of type 2 diabetes.[130]
A history of GDM is considered a cardiovascular risk factor by the AHA and provides an opportunity for early cardiovascular risk surveillance modification.[130][139]
The AHA advises that the postpartum and interpregnancy time frames are critical time windows in which implementation of a comprehensive multidisciplinary plan and careful consideration of cardiovascular risk factors are important to reduce adverse maternal outcomes.[115]
In the UK, the NHS Diabetes Prevention Programme can support patients with lifestyle change interventions. Patients can be referred by their GP or self-refer.[137]
In addition to lifestyle interventions such as diet and exercise, weight loss treatment may include pharmacological options, such as glucagon-like peptide-1 (GLP-1) receptor agonists, or bariatric surgery for eligible patients.
Use of this content is subject to our disclaimer