GDM

Question 1

GDM risk factors

Answer 1

GDM in previous pregnancy
Previous baby >4.5kg
BMI >30
PCOS
FHx of DM
South Asian ethnicity

Question 2

GDM incidence

Answer 2

10-15%

Question 3

What is the pathophysiology of GDM?

Answer 3

Placenta produces human placental lactogen (hPL)
Increases insulin resistance and changes carbohydrate metabolism
= High blood glucose

Question 4

Describe the OGTT

Answer 4

Fast overnight - measure fasting blood glucose

Give 75mg oral glucose - 2h later measure blood glucose

Question 5

What are the diagnostic criteria for GDM?

Answer 5

Fasting blood glucose ≥5.6mmol/L

2h OGTT ≥7.8mmol/L

Question 6

What other blood glucose measurement is useful to look at in GDM?

Answer 6

HbA1c (check <48mmol/L to rule out existing DM)

Question 7

How do we screen for GDM?

Answer 7

Risk factors should be identified at booking (previous GDM, BMI >30, SA, previous baby >4.5kg, FHx of DM)
If woman has previous GDM: OGTT at booking, repeat at 28w
If risk factors: OGTT at 24-28w
All women: OGTT at 28w

Question 8

Where should a woman diagnosed with GDM be managed?

Answer 8

Refer to obs endo clinic - MDT care plan with obstetrician, dietician, specialist midwife

Question 9

How is it best to explain GDM to patient?

Answer 9

• Explain why GDM occurs (placenta produces hormones that increase blood sugar levels)
• This can have short / long term complications for mum + baby
• Good BG control reduces risks - this is achieved by monitoring and making lifestyle changes / using medication if needed

Question 10

What are the main points in managing GDM?

Answer 10

Will be under care of obs endo clinic

• Self-monitoring BG (monitor, 7x daily, targets)
• Keeping BG low (exercise, diet, medications)
• Antenatal/intra-partum/post-partum care

Question 11

Self-monitoring of BG

Answer 11

• Capillary BG monitor + record results
• 7x daily - waking, post-breakfast, pre-dinner, post-dinner, pre-tea, post-tea, pre-bed
• Targets pre-meal 5.3 / 1h post-meal 7.8 / 2h post-meal 6.4

Question 12

Keeping BG low

Answer 12

• Regular exercise ‘absorbs sugar from blood’
• Dietary changes (low GI - dietician input)
• Medical therapy as required (metformin / sc insulin)

Question 13

What determines whether medical therapy is needed?

Answer 13

Fasting plasma glucose. If <7mmol/L you trial lifestyle changes for 2w, then give metformin if targets not met, and insulin if targets still not met. If >7mmol/L or >6mmol/L with complications, diet + exercise + insulin straight away (+/- metformin)

Question 14

What are the mechanisms of metformin and insulin?

Answer 14

Metformin decreases hepatic glucose production

Insulin drives glucose into cells

Question 15

What can be given if metformin insufficient and insulin declined?

Answer 15

Glibenclamide

Question 16

Antenatal / intra-partum / post-partum care

Answer 16

• Antenatal: Obs endo clinic every 2w, serial ‘extra’ growth scans (28, 32 + 36w)
• Intra-partum: timing <40+6w (may need induction / C-section), will need to be admitted to monitor capillary glucose during labour + resuscitate baby if needed (hypo)
• Post-partum: neonate (monitor for hypoglycaemia), mum (monitor for T2DM)

Question 17

What are the maternal + fetal complications of GDM?

Answer 17

• Maternal: most will get no symptoms but some do; 1 in 3 will develop T2DM in 5y; increased risk in future pregnancies; delivery may require IOL/C-section, big baby tears, pre-eclampsia
• Fetal: post-natal hypo; macrosomia >4kg (shoulder dystocia), still birth >40+6