Continuing our series highlighting recent presentations from Nursing in Practice 365 events, diabetes specialist midwife Cathy Jones and diabetes specialist dietitian Shweta Patel outline some key points about gestational diabetes for nurses in primary care.
What is gestational diabetes?
Gestational diabetes mellitus (GDM) is where diabetes is detected at first onset or recognized for the first time during pregnancy. It is a common complication of pregnancy, due to hormonal changes that can increase the risk of insulin resistance.
Anyone can develop GDM but we screen some pregnant women for GDM if they are at high risk. This includes anyone with a body mass index (BMI) over 30, who has had GDM in a previous pregnancy, with a parent or sibling with diabetes or who is of south Asian, Black, African-Caribbean or Middle Eastern origin.
What are the risks from developing GDM?
The risks of GDM to mother and baby include the baby being large for gestational age, shoulder dystocia, premature birth and stillbirth.
For mothers, GDM significantly increases their risk of developing type 2 diabetes mellitus (T2DM), with 50% of those with GDM developing T2DM within 5-10 years. As a consequence, following their pregnancy, they should undergo annual HbA1c tests in primary care, to ensure pre-diabetes or T2DM is detected early and managed appropriately.
How is it diagnosed?
Glucose levels in pregnancy differ from outside of pregnancy and diagnosis of GDM is usually based on an oral glucose tolerance test (OGTT) rather than HbA1c levels. The OGTT essentially measures blood glucose levels after fasting and then 2 hours after taking a glucose drink.
Diagnostic values differ between different sets of guidelines and values also vary to some extent across regions for diagnosis, but NICE says GDM should be diagnosed if the woman has either:
- a fasting plasma glucose level of ≥6 mmol/L or
- a 2‑hour plasma glucose level of ≥8 mmol/L.
Most women who develop GDM will be picked up through the screening process. Some women who are not screened may go on to develop GDM during pregnancy, however, so it is important for all pregnant women to be monitored for any potential symptoms or signs of diabetes during their antenatal check-ups, so they can be referred promptly to the specialist diabetes antenatal clinic if needed. This includes routine urine dipstick tests to check for glycosuria.
Any woman who has an HbA1c test indicating they have pre-diabetes, or overt T2DM, during pregnancy will also need direct referral to the specialist diabetes antenatal clinic to ensure they have appropriate follow-up tests and specialist care.
In addition, anyone with pre-existing T2DM who is planning to have a baby or is pregnant should be referred promptly to the specialist service so they can be counselled fully about changes to their diet and medication.
What are the main approaches to management of GSM?
Dietary and lifestyle changes are advised during pregnancy and postnatally alongside breastfeeding. Primary care nurses can provide support by encouraging women to follow advice given at the diabetes antenatal clinic. They can also be proactive and encourage a healthy diet and lifestyle in all pregnant women to help prevent GDM.
Some women with GDM manage to control glucose levels with dietary and lifestyle changes alone, while others may require medications. Elevated fasting glucose levels are not usually associated with diet and will require medication. If someone requires treatment, metformin and insulin are currently the only recommended medications.
A healthy, balanced diet can help keep glucose levels in the recommended range during pregnancy; for those diagnosed with GDM this should be supported by a specialist dietitian.
Keeping physically active on a daily basis also helps to manage glucose levels. Advise patients to aim for 30 minutes of exercise a day. This could include encouraging individuals to walk after meals, to help post-meal glucose rises stay within the recommended range.
What dietary changes are advised with GDM?
It’s important to understand that carbohydrates provide a key source of energy, but all carbohydrates that we eat or drink break down into glucose. The amount of carbohydrate and type of carbohydrate consumed can both make a difference to glucose levels and management of GDM.
Carbohydrates should be included with every meal, but foods lower on the glycaemic index (GI) – a measure of how a food affects blood sugar levels – are advised in managing GDM, as these cause a slow rise in glucose levels; they also generally tend to be higher in fibre.
Some other key dietary pointers:
- Fruit is best consumed in-between meals as snacks and avoid fruit juices and smoothies.
- Swap sugary drinks and foods for sugar-free varieties where possible (use sweeteners instead of sugar; diet or zero drinks are better than sugary versions). Other forms of sugar such as honey and jaggery will cause glucose levels to rise and should be avoided.
- Carbohydrate portions should be around a fist size per mealtime. Adding protein at each meal will also help to feel fuller for longer and reduce the GI of a meal. This will not only help manage glucose levels but also avoid excess weight gain in pregnancy.
- It is important to be healthy but not restrictive – we advise women against going to extremes of limiting their carbohydrate intake or cutting it out altogether; it’s all about making healthy dietary changes both for now and the future.
A healthy lifestyle and diet during pregnancy will not only help to control the GDM but also reduce the patient’s future risk of developing T2DM. The recent DiGEST study showed that, among women with GDM who had a BMI of 25kg/m2 or above, a reduced calorie diet in the third trimester of pregnancy was linked to less need for long-acting insulin.
Cathy Jones is a diabetes specialist midwife and Shweta Patel is a diabetes specialist dietitian at University Hospitals of Leicester NHS Trust
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