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Gestational Diabetes

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Overview

Definition

Diabetes: A group of metabolic diseases in which there are high blood sugar levels over a prolonged period. Two types Diabetes Mellitus Type I (autoimmune destruction of beta cells in the pancreas) and Type II (insulin resistance followed by beta cell atrohpy)

Gestational Diabetes: diabetes diagnosed during the second half of pregnancy with no prior existing diabetes.

Affects 5-10% of pregnancies. Incidence varies between nutritional and genetic factors. Risk of GDM increases with age. Women born in Southern Asia are at particularly higher risk. 50% change of mother to develop Type II Diabetes later in life.

Pregnancy Physiology

Watch Physiology Changes in Pregnancy

Aetiology and Risk Factors

Risk Factors
Previous GDM
Increase BMI
Maternal age >40yo
Family history
Polycystic ovarian syndrome
Low fibre diet
Weight gain as young adult
Current use of glucocorticoids and antipsychotics?

Pathophysiology

Normal Physiology

  • Maternal metabolism switches from carbohydrates to fat utilisation
  • Subsequent pancreatic beta cell hyperplasia
  • Increased insulin secretion
  • Early increase in insulin sensitivity causes progressive insulin resistance.

Pathophysiology

  • Placenta produces growth hormone, CRH,  placental lactinogen and progesterone.
  • These hormones promote glucose intake by the fetus by causing insulin resistance in the mother
  • Hyperglycaemia in circulation eventually cause the release of fetal insulin causing insulinaemia

Clinical Manifestation

Clinical Presentation generally asymptomatic

Classic signs of Type II Diabetes (4P’s)

  • Polyphagia
  • Polydipsia
  • Parasaethsia
  • Polyuria

Investigations

Screening/Diagnosis

In Australia oral glucose tolerance test (75g) at 24 and 28weeks.

  • Test at 1 hour >10 or 2 hour >8.5
  • Fasting glucose 5.1 hour
Diagnosing diabetes mellitus in pregnancy: The 7/11 rule. Fasting plasma glucose >7mmol/L and random BGL >11 mmol/L with symptoms of diabetes mellitus.
Remember it is important to test for gestational diabetes because it can cause congenital abnormalities, miscarriages,  organomegaly, hydramnios, pre-eclampsia, maternal and infant birth trauma, perinatal mortality and neonatal metabolic and respiratory problems.

Treatment

Diagnosis GDM then management of a multidisciplinary team (i.e endocrinologist, diabetic educator).

  • Monthly ultrasound to check for foetal macrosomia.
  • Diet, exercise and blood glucose monitoring.
  • If glucose unstable change to insulin.
  • Induction of labour if continuously unstable gestational diabetes before term or early at term – to prevent complications
  • Postpartum (after delivery) stop insulin and glucose infusions, check blood glucose prior to discharge, follow up 6 weeks for oral glucose tolerance test, educate (as 50% risk of developing diabetes mellitus over the next 25years).
Remember Why treat GDM? Reduction in composite outcome of death, shoulder dystocia, bone fracture and nerve palsy. Reduction in infants weighing >90th birth-centile.

Complications and Prognosis

Video: Gestational Diabetes
Watch Video Gestational Diabetes – DETAILED Overview (Pathophysiology and Complications)

Discussion

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