Gestational Diabetes

This is the second most common medical complication in pregnancy after high blood pressure.

– It is defined as any degree of glucose intolerance with onset/first recognition during pregnancy

– In pregnancy, there is progressive insulin resistance which means a higher volume of insulin is needed to respond to a normal level of blood glucose

– A woman with a borderline pancreatic reserve is unable to respond to the increased insulin requirement

– This results in transient hyperglycaemia giving gestational diabetes

– After the pregnancy, insulin resistance falls and the hyperglycaemia usually resolves

– However, whilst it is usually asymptomatic usually, it can lead to complications for the fetus

Risk factors:

– BMI>30

– Past medical or family history of diabetes

– Asian/Black

Symptoms:

– Usually asymptomatic but can give hyperglycaemic symptoms(polyuria, polydipsia and fatigue)

The problem is that in pregnancy, glucose is transported across the placenta, but insulin is not.

– Therefore, high level of glucose in the maternal circulation can cause foetal hyperglycaemia

– In response, the fetus will increase its own insulin, resulting in hyperinsulinemia

– Insulin has a similar chemical structure to growth factors which promotes growth leading to complications.

Complications:

Antenatal:

– Macrosomia, increasing risk of shoulder dystocia and labour complications (perineal tears)

– Organomegaly (especially cardiomegaly with cardiomyopathy)

– Polycythaemia

– Microsomia (due to poor placental vasculature)

– Decreases foetal surfactant production giving risk of transient tachypnoea of new-born

Postnatal:

–  After delivery, fetus still has high insulin levels but no longer receives maternal glucose

– This results in an increased risk of hypoglycaemia

Diagnosis:

– Oral glucose tolerance test (measure blood glucose 2 hours after 75g glucose drink)

– Positive result if fasting glucose >5.6mM or OGTT glucose >7.8mM

Management:

This involves management of the blood sugar as well as steps to ensure a safe pregnancy:

Diabetic Control:

– If fasting glucose <7mM on diagnosis:

–> Diet control and exercise

– If glucose targets not met within 2 week:

–> Commence metformin

– If still uncontrolled Or fasting glucose >7mM on diagnosis Or 6-6.9mM + foetal complications:

–> Commence metformin and Insulin

Pregnancy:

– Antenatal:

–> Additional growth screen from week 28 to monitor macrosomia/polyhydramnios 

– Delivery:

–> Women typically deliver earlier than 40 weeks due to the macrosomia                

– Postnatal:

–> Mother stops all diabetes medication immediately after delivery and OGTT few months after

–> You can also keep the baby in hospital for 24 hours to monitor for neonatal hypoglycaemia