Gestational Diabetes

Question 1

Define Gestational Diabetes, and why does it happen?

Answer 1

Abnormal glucose tolerance that develops during pregnancy, leading to abnormal glucose levels.

Occurs speifically during pregnancy as the hormones the placenta produces; cortisol, placental lactogen, progesteron, HCG are antagonistic to insulin, which in women who are already insulin resistent or at high risk→ hyperglycaemia → GDM

Question 2

What is the difference of screening vs a diagnostic test

Answer 2

Screening:

• To detect early disease or risk factors
• Offered to everyone
• Not definative, offersa risk level which can determine the suitability of dx testing

Diagnostic:

• Confirms presence/absence of disease
• Offered to those with + screening
• Definative diagnosis

Question 3

What is the Screening Test for GDM in NZ?

Answer 3

All women are offered a HbA1c test at 20weeks gestation.

• >50mmol/ml: probable undiagnosed GDM → refer to diabetes services
• 41-49mmol/mL: High risk of developing GDM/prediabetic → offer OGTT at 24-28weeks + advise healthy lifestyle/exercise til then
• <40mmol/mL: normal → still offer GCT/polycose test at 24-28weeks

Question 4

How does the GCT/Polycose test work

Answer 4

1. Non-fasting 50g oral glucose given
2. Measure blood glucose 1hr after
   
   • <7.8 normal
   • >7.8 refer for OGTT
   • >11.1 refer to diabetes services

Question 5

What is the Diagnostic Test for GDM?

Answer 5

Oral Glucose Tolerance Test (OGTT)

1. Fast for 8hrs
2. Measure BG (>5.5mmol/mL bad)
3. then have 75g oral glucose
4. measure BG after 2 hours (>9.0mmol/mL bad)

**If Fasting blood glucose _>_5.5mmol/L or 2hr blood glucose _>_9.0mmol/L = GDM

Question 6

What are the two main circumstances OGTT would be offered?

Answer 6

If the HbA1c (screening) was 41-49mmol/mL

OR

if the GCT/polycose test was >7.8mmol/L

Question 7

What is HbA1c?

Answer 7

Average measure of the glycated Hb over the last 8 weeks

Question 8

Pros of HbA1c as a screening tool?

Answer 8

• Cheap
• No fasting needed
• Can be offered at any time of the day
• Not imapcted by acute factors (exercise, stress, diet etc)
• Minimal biological variability
• Reflects long term BG

Is a reliable tool for earlier detection of disease or disease identification

Question 9

Cons of HbA1c as a screening tool for GDM?

Answer 9

• Measures glycated Hb not blood glucose
• HbA1c can change with some conditions (eg; drops in anaemia)
• Can falsely drop in pregnancy (as RBC production increases glycosylation of Hb decreases)
• Could cause unneccessary anxiety/excessive exercise
• Not diagnostic
• No evidence of benefit as of yet

Question 10

Targets for diabetes management during pregnancy, and what happens if these aren’t met?

Answer 10

• Fasting Glucose Target: <5.5mmol/mL
• After 1 hr postprandial: <7.4mmol/mL
• After 2hr postprandial: <6.7mmol/mL

If these aren’t met >90% of the time then medication (metformin and/or insulin) is required to manage the GDM

Question 11

Is fetal growth as assessed by USS a reliable method to guide GDM treatment?

Answer 11

No as it is variable by +/- 10%

(this is why GROW charts are done maximally every 2/52)

Question 12

For a GDM patient, when will delivery occur

Answer 12

• If growth at 36-37 weeks is <90^th centile : 40 weeks
• If growth at 36-37 weeks is >90^th centile OR maternal complications occur (PET, hypertension, macrosomia, >40 maternal age) : 38-39 weeks

Question 13

Post partum follow up for GDM patient?

Answer 13

• Check HbA1c at 3 months postpartum
• Then check annually

This is because these patients are at an increased risk of T2DM

Question 14

Short term and long term impact of GDM on the mother

Answer 14

Short term

• PET
• Preterm labour
• c-section or instrumental delivery (macrosmic baby)
• Induction
• Birth Trauma
• PPH
• Infection
• if pre-existing diabetes then worsening retinopathy, DKA, nephropathy

Long Term:

• T2DM
• Diabetes related vascular disease

Question 15

Short and long term impact of GDM on the fetus

Answer 15

Short Term:

• LGA
• Polyhydraminos
• Organomegaly
• Unstable lie, malpositioning
• shoulder/labour dystocia
• Fetal Growth Restriction (due to hyperinsulinaemia)
• PTL
• Stillbirth
• Neonatal morbidity ((hypoglycaemia, hyperbilirubinemia, hypocalcemia, hypomagnesemia, polycythemia, respiratory distress, cardiomegaly)

Long Term:

• Obesity
• Impaired glucose tolerance/T2DM
• Metabolic syndrome

Question 16

Risk factors for developing T1DM, T2DM and GDM

Answer 16

Question 17

How can you diminish the risk factors for T1DM, T2DM and GDM?

Answer 17

• T1DM: you cant
• T2DM
  
  • Healthy lifestyle/diet, reduce calorie intake
  • Exercise (aerobic encouraged)
  • Stop smoking
  • Self monitor BG regularly
  • Education on diabetes/disease management
• GDM:
  
  • Same as T2DM except encourage moderate exercise
  • **also give info on appropriate gestational weight gain

Question 18

What is a normal/appropriate amount of weight to gain in pregnancy?

Answer 18

Question 19

How would you counsel a woman who has Type II diabetes and wishes to become pregnant?

Answer 19

• Educate her about the importance of glucose control, the effects of excess glucose on baby’s development, and complications that can occur.
• Educate and encourage her that keeping good glucose control during pregnancy has a good prognostic outcome for the baby.
• Advise her to use contraception until her HbA1c is within a normal range (reduces risk of baby being affected by excess glucose, such as stillbirth, congenital abnormalities. Also reduces risk of complications to mother)
• Advise taking increased folic acid (5mg OD)
• Discontinue statins, ACE inhibitors or ARBs (teratogenic)
• Discuss screening and treating for T2DM complications before conceiving – retinopathy, nephropathy, cardiovascular disease…etc

Question 20

Under what circumstances might you consider testing glucose tolerance prior to pregnancy?

Answer 20

• Women who have had prior GDM and are wanting to get pregnant
• Women with a high risk for undiagnosed diabetes or GDM (look at risk factors)