Treatments
Conventionally, gestational diabetes is treated with dietary and lifestyle management, with the addition of supplementary insulin if acceptable glycaemic levels are not achieved (Fraser, 2009).
NICE (2008) recommend treatment with lifestyle modification (diet and exercise) for 1–2 weeks; in patients with a BMI >27 kg/m², they suggest calory restriction and moderate exercise.Blood glucose-lowering therapy should be considered if near-normal glucose levels are not achieved or if macrosomia is evident or suspected from an ultrasound scan. Guidance suggests clinically effective diabetes therapy includes oral antidiabetes drugs (metformin and glibenclamide) and insulin therapy using human insulin or rapid-acting analogues, which should be tailored to individual glycaemic profiles. Glycaemic targets for gestational diabetes mirror those for women with pre-gestational diabetes and women should be asked to monitor their blood glucose levels pre- and 1 hour post-meal. The targets to aim for are fasting blood glucose levels of 3.5–5.5 mmol/litre and a 1-hour post-meal glucose below 7.8 mmol/litre (NICE, 2008).
However, it is important to remember that no oral hypoglycaemic agent or insulin is licensed for use in pregnancy. Fraser (2009) identifies that oral hypoglycaemic agents are not generally used, principally owing to concerns in relation to transplacental passage and risk of neonatal hypoglycaemia. In addition, there have been concerns that oral hypoglycaemic agents do not offer the same quality of glycaemic control as insulin.
Lifestyle modificaton
Following diagnosis, the woman should be taught how to self-monitor blood glucose levels with the aid of a glucose meter; strips for self-monitoring are available on FP10 prescription, and appropriate glucose targets should be discussed and recorded. Typically, glucose measurements are requested pre-breakfast and 1 hour post-meals. If three consecutive readings outside of the target range are recorded, the women is encouraged to contact their health professional, as they may require supplementary glucose-lowering therapy.
Diet and lifestyle advice should include the need to avoid all ‘added’ sugar foods and drinks and the need to incorporate more long-acting, low glycaemic index carbohydrates as part of the normal diet. The main goal of dietary modification is to avoid or minimize post - prandial peaks in glucose levels. Moderate exercise is encouraged, although there is no identified evidence as to type, frequency, or effect.
Metformin
Metformin is from the biguanide class of drugs. It was first synthesised in the 1920s and found to reduce blood glucose levels. Metformin has been found to activate adenosine monophosphate-activated protein kinase—an enzyme that plays an important role in insulin signalling and the metabolism of glucose and fats. It is contraindicated in people who are at risk of lactic acidosis and those with liver or renal disease.
Metformin works by suppressing gluconeogenesis in the liver, increasing insulin sensitivity and enhancing peripheral glucose uptake. It has been found to be weight neutral. Hyer et al (2009) suggest that, as metformin improves insulin sensitivity, it can therefore be expected to improve glucose tolerance in pregnancy by reducing the physiological rise in insulin resistance that occurs during pregnancy. Metformin does not cause hypoglycaemia or weight gain and is therefore the first-line drug of choice (after lifestyle modification) in obese women with gestational diabetes. Metformin is known to have gastrointestinal side effects, but, for many women, taking a tablet is more acceptable than self-injecting insulin, and free from the risk of hypoglycaemia (Fraser, 2009). Metformin is not metabolised; it is cleared from the body by tubular secretion in the kidneys and excreted unchanged in the urine. The elimination half life is just over 6 hours.
Metformin appears to have some advantages over other treatment modalities. As suggested by Fraser (2009), it has been shown to be effective in achieving glycaemic control in some women; however, Fraser (2009) suggests that up to 40% of women treated with metformin will require supplementary insulin to maintain glycaemic targets.
Rowan et al (2011) considered the offspring follow-up from MiG and identified that metformin crossed the placenta in significant amounts, further adding that while neonatal outcomes were reassuring it is important to examine long-term outcomes, such as body composition, in childhood.
Her research concluded that ‘maternal metformin treatment during pregnancy may lead to a more favourable pattern of fat distribution for exposed children’ (Rowan et al, 2011).
However, despite efficacious evidence, the use of metformin in pregnancy remains unlicensed, and therefore patients and GPs should be given written information clearly stating this fact. In addition, women should have the right to refuse treatment with this drug for this reason.
Glibenclamide
Glibenclamide is a sulphonylurea that improves glucose control by acting on insulin secretion and insulin action. It stimulates insulin release by beta-cells through the increase of intracellular calcium. Its main side effect, in conjunction with other sulphonylureas, is hypoglycaemia.
The primary action of sulphonylureas is to increase insulin secretion, and therefore decrease hepatic glucose toxicity and create an indirect improvement in insulin sensitivity. Glibenclamide was not detected in cord serum and its addition had no effect on the placental transport and uptake of glucose. The use of oral sulphonylureas in pregnant women has been limited, and therefore there is scant information on their efficacy.
Langer et al conducted a study in 404 women randomised to either glibenclamide or insulin. Both groups had similar outcomes; cord insulin levels showed no significant difference and there was no difference in respiratory distress syndrome or neonatal hypoglycaemia. In addition, glibenclamide was not detected in the cord blood, which explains the absence of neonatal hypoglycaemia.
TreatmentsConventionally, gestational diabetes is treated with dietary and lifestyle management, with the addition of supplementary insulin if acceptable glycaemic levels are not achieved (Fraser, 2009). NICE (2008) recommend treatment with lifestyle modification (diet and exercise) for 1–2 weeks; in patients with a BMI >27 kg/m², they suggest calory restriction and moderate exercise.Blood glucose-lowering therapy should be considered if near-normal glucose levels are not achieved or if macrosomia is evident or suspected from an ultrasound scan. Guidance suggests clinically effective diabetes therapy includes oral antidiabetes drugs (metformin and glibenclamide) and insulin therapy using human insulin or rapid-acting analogues, which should be tailored to individual glycaemic profiles. Glycaemic targets for gestational diabetes mirror those for women with pre-gestational diabetes and women should be asked to monitor their blood glucose levels pre- and 1 hour post-meal. The targets to aim for are fasting blood glucose levels of 3.5–5.5 mmol/litre and a 1-hour post-meal glucose below 7.8 mmol/litre (NICE, 2008). However, it is important to remember that no oral hypoglycaemic agent or insulin is licensed for use in pregnancy. Fraser (2009) identifies that oral hypoglycaemic agents are not generally used, principally owing to concerns in relation to transplacental passage and risk of neonatal hypoglycaemia. In addition, there have been concerns that oral hypoglycaemic agents do not offer the same quality of glycaemic control as insulin.Lifestyle modificatonFollowing diagnosis, the woman should be taught how to self-monitor blood glucose levels with the aid of a glucose meter; strips for self-monitoring are available on FP10 prescription, and appropriate glucose targets should be discussed and recorded. Typically, glucose measurements are requested pre-breakfast and 1 hour post-meals. If three consecutive readings outside of the target range are recorded, the women is encouraged to contact their health professional, as they may require supplementary glucose-lowering therapy. Diet and lifestyle advice should include the need to avoid all ‘added’ sugar foods and drinks and the need to incorporate more long-acting, low glycaemic index carbohydrates as part of the normal diet. The main goal of dietary modification is to avoid or minimize post - prandial peaks in glucose levels. Moderate exercise is encouraged, although there is no identified evidence as to type, frequency, or effect.MetforminMetformin is from the biguanide class of drugs. It was first synthesised in the 1920s and found to reduce blood glucose levels. Metformin has been found to activate adenosine monophosphate-activated protein kinase—an enzyme that plays an important role in insulin signalling and the metabolism of glucose and fats. It is contraindicated in people who are at risk of lactic acidosis and those with liver or renal disease. Metformin works by suppressing gluconeogenesis in the liver, increasing insulin sensitivity and enhancing peripheral glucose uptake. It has been found to be weight neutral. Hyer et al (2009) suggest that, as metformin improves insulin sensitivity, it can therefore be expected to improve glucose tolerance in pregnancy by reducing the physiological rise in insulin resistance that occurs during pregnancy. Metformin does not cause hypoglycaemia or weight gain and is therefore the first-line drug of choice (after lifestyle modification) in obese women with gestational diabetes. Metformin is known to have gastrointestinal side effects, but, for many women, taking a tablet is more acceptable than self-injecting insulin, and free from the risk of hypoglycaemia (Fraser, 2009). Metformin is not metabolised; it is cleared from the body by tubular secretion in the kidneys and excreted unchanged in the urine. The elimination half life is just over 6 hours. Metformin appears to have some advantages over other treatment modalities. As suggested by Fraser (2009), it has been shown to be effective in achieving glycaemic control in some women; however, Fraser (2009) suggests that up to 40% of women treated with metformin will require supplementary insulin to maintain glycaemic targets. Rowan et al (2011) considered the offspring follow-up from MiG and identified that metformin crossed the placenta in significant amounts, further adding that while neonatal outcomes were reassuring it is important to examine long-term outcomes, such as body composition, in childhood. Her research concluded that ‘maternal metformin treatment during pregnancy may lead to a more favourable pattern of fat distribution for exposed children’ (Rowan et al, 2011). However, despite efficacious evidence, the use of metformin in pregnancy remains unlicensed, and therefore patients and GPs should be given written information clearly stating this fact. In addition, women should have the right to refuse treatment with this drug for this reason.GlibenclamideGlibenclamide is a sulphonylurea that improves glucose control by acting on insulin secretion and insulin action. It stimulates insulin release by beta-cells through the increase of intracellular calcium. Its main side effect, in conjunction with other sulphonylureas, is hypoglycaemia. The primary action of sulphonylureas is to increase insulin secretion, and therefore decrease hepatic glucose toxicity and create an indirect improvement in insulin sensitivity. Glibenclamide was not detected in cord serum and its addition had no effect on the placental transport and uptake of glucose. The use of oral sulphonylureas in pregnant women has been limited, and therefore there is scant information on their efficacy. Langer et al conducted a study in 404 women randomised to either glibenclamide or insulin. Both groups had similar outcomes; cord insulin levels showed no significant difference and there was no difference in respiratory distress syndrome or neonatal hypoglycaemia. In addition, glibenclamide was not detected in the cord blood, which explains the absence of neonatal hypoglycaemia.
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