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Gestational Diabetes

Gestational diabetes is any degree of glucose intolerance with its onset or first diagnosis during pregnancy, and usually resolving shortly after delivery. It is thought that hormones associated with pregnancy increase post prandial glucose concentrations and insulin resistance. This is normally countered by an increase in insulin production, but in gestational diabetes, the compensatory rise is insufficient. Gestational diabetes usually develops in the third trimester. Up to 5% of women giving birth in the UK have either pre?existing diabetes or gestational diabetes. Of women who have diabetes during pregnancy, it is estimated that approximately 87.5% have gestational diabetes (which may or may not resolve after pregnancy), 7.5% have type 1 diabetes and the remaining 5% have type 2 diabetes. The prevalence of type 1 diabetes, and especially type 2 diabetes, has increased in recent years. The incidence of gestational diabetes is also increasing as a result of higher rates of obesity in the general population and more pregnancies in older women. Diabetes in pregnancy is associated with risks to the woman and to the developing fetus. Miscarriage, pre-eclampsia and preterm labour are more common in women with pre-existing diabetes. In addition, diabetic retinopathy can worsen rapidly during pregnancy. Stillbirth, congenital malformations, macrosomia, birth injury, perinatal mortality and postnatal adaptation problems (such as hypoglycaemia) are more common in babies born to women with pre-existing diabetes. The risk of developing gestational diabetes is assessed using risk factors in a healthy population. At the initial assessment, determine the following:

  • BMI above 30 kg/m2
  • Previous macrosomic baby weighing 4.5 kg or more
  • Previous gestational diabetes
  • Family history of diabetes (first degree relative)
  • Minority ethnic family origin with a high prevelance of diabetes.
The National Institute for Health and Care Excellence (NICE) guideline states fasting plasma glucose, random blood glucose, HbA1c, glucose challenge test or urinalysis for glucose should not be used to assess risk of developing gestational diabetes. Gestational diabetes is diagnosed if the woman has a fasting plasma glucose level of 5.6 mmol/l or above, or a 2-hour plasma glucose level of 7.8 mmol/l or above.

Management is initially with dietary and lifestyle changes but if these have not reduced blood glucose to acceptable levels (less than 7.0 mmol/l) within 1 - 2 weeks, treatment should be with metformin and/or insulin. Treatment should be discontinued immediately after delivery, but women should have a fasting plasma glucose test 6-13 weeks after birth to exclude diabetes.

Women with gestational diabetes should give birth no later than 40+6 weeks, and should be offered induction of labour or caesarean section if they have not delivered by this time.

Further reading

National Institute for Health and Care Excellence (2015). NG3. Diabetes in pregnancy: management from preconception to the postnatal period. Available at:

Tidy C. (2015) Gestational diabetes (Professional reference). Available at:

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