Diabetes in pregnancy

Question 1

Definition of gestational diabetes

Answer 1

• Any degree of glucose intolerance with onset or first recognition during pregnancy
• May or may not resolve after pregnancy

Question 2

Aetiology of gestational diabetes

Answer 2

• Physiological insulin resistance during pregnancy + insufficient pancreatic compensation
  
  • Placental hormones (lactogen, progesterone, cortisol)
    
    • Antagonistic effects on insulin ↑ glucose availability

Question 3

Complications of diabetes in pregnancy

• Maternal
• Obstetric
• Foetal
• Neonatal

Answer 3

Maternal

• Hypoglycaemia
  
  • Tight regulation of serum glucose concentration
• Complications of uncontrolled diabetes
  
  • Ketoacidosis
  • Retinopathy
  • Nephropathy
  • Neuropathy

Obstetric

• Preterm labour
• Miscarriage
• Obstructed labour
  
  • Shoulder dystocia
  • Neuropathy
• ↑ likelihood of caesarean section
• ↑ risk of thromboembolism
• ↑ risk of maternal infection

Foetal

• Intrauterine death (stillbirth)
• Congenital malformation
  
  • CNS (neural tube)
    
    • Anencephaly
    • Spina bifida
    • Sacral agenesis (caudal regression syndrome)
      
      • Almost exclusive to diabetic offspring, but RARE
  • Cardiac
• Hyperinsulinaemia (pancreatic islet cell hyperplasia)
  
  • Foetal macrosomia
    
    • Shoulder dystocia / birth trauma
    • Foetal distress during labour
  • Polyhydramnios (↑ metabolic rate → ↑ urine output)
• Impaired foetal growth
  
  • Due to maternal vascular disease (including placental vasculature)

Neonatal

• Hypoglycaemia (hyperinsulinaemia)
• Respiratory distress syndrome (↓ foetal lung maturity)
• Polycythaemia (hypoxia caused by maternal vascular disease)
  
  • ↑ viscosity of blood
    
    • Stroke, seizures, necrotizing enterocolitis, renal vein thrombosis
  • Hyperbilirubinaemia → Jaundice
• Metabolic disturbances

Question 4

Screening for gestational diabetes

• Risk factors

Answer 4

NICE guidelines recommend screening women with any of the following risk factors for GDM:

• BMI >30
• Previous macrosomic baby weighing >4.5 kg
• Previous GDM
• Family history of DM
• Family origin in an area with high prevalence of DM

Screening involves oral glucose tolerance test (OGTT) at 28 weeks (18 weeks if previous GDM)

Question 5

Monitoring during diabetes in pregnancy

• Glycaemic control

Answer 5

• Blood glucose levels
  
  • Check up every 2 weeks up to 34 weeks, weekly thereafter
    
    • Preconception
      
      • Maintain target HbA1c < 6.1% (7.1 mmol/L)
    • Antenatal
      
      • Fasting glucose
      • 1 hour postprandial blood glucose
• Retinal screening
• Renal function
• Foetal echocardiography (in additon to normal scans)

Question 6

Management of gestational diabetes

Answer 6

• Diet & exercise
• Oral hypoglycaemic agents
  
  • Metformin
    
    • ↑ insulin sensitivity
    • ↓ hepatic glucose production
    • ↓ intestinal absorption of glucose
  • Glibenclamide (sulphonylurea)
    
    • ↑ insulin secretion
• Insulin (cannot cross the placenta)
• Offer induction at 38 weeks
  
  • Sliding scale insulin and dextrose infusion during labour

Question 7

Preconception advice for women with diabetes

Answer 7

• Diabetes can affect the health of both mother and baby
• Target HbA1c < 43 mmol/mol (6.1%)
  
  • Reduce the risk of congenital malformations
• Diet, weight and exercise can reduce complications
• Risks of hypoglycaemia and its unawareness in pregnancy
• Effect of nausea and vomiting on glycaemic control
• Increased risk of having a large baby, associated complications (birth trauma, induction of labour, Caesarean)