Tutorial 5: Gestational Diabetes Mellitus

Question 1

What is the gestational diabetes mellitus?

Answer 1

Gestational diabetes mellitus is defined as abnormal glucose tolerance that is detected or develops in pregnancy.

• Similar pathogenesis to T2DM
• Many are at increased risk of developing T2DM subsequently.

GDM develops due to an abnormal glucose metabolism. Occurs when insulin production is inadequate.

• Discovery of type II DM is not uncommon during pregnancy but rare for type I.
• Endocrine changes during pregnancy may mean a transient self-limiting state of hyperglycemia.

Question 2

What is the difference between Type I and Type II diabetes mellitus?

Answer 2

• Type 1 DM: Insulin Dependant DM
  
  • Absolute insulin deficiency.
  • Autoimmune destruction of pancreatic Beta-cells.
  • Exogenous insulin is required to prevent ketoacidosis.
• Type 2 DM- Insulin Resistant DM
  
  • Insulin is relatively deficient due to inadequate compensation for underlying insulin resistance.
  • Central adiposity and elevated insulin levels are common
  • but the action of insulin is impaired due to many factors eg. Interactions with adipocytokines.

Question 3

How is glucose homeostasis maintained?

Answer 3

Glucose homeostasis maintained by balance of insulin and other hormones such as glucagon and cortisol.

Question 4

How is pregnancy a diabetogenic environment?

Answer 4

1. Placenta produces:
   
   1. Additional Cortisol
   2. Other insulin antagonists, which have a tendency to increase maternal blood glucose.​
      
      • hpl Human placental lactogen
      • Progesterone
      • hCG human chorionic gonadotrophin
2. Pancreatic beta islet cells:
   
   1. unable to produce sufficient insulin to balance this increase of maternal blood glucose level
   2. and/or there is maternal insulin resistance, the mother may develop a state of hyperglycemia “gestational diabetes.”

Question 5

What is impaired glucose tolerance during pregnancy?

Answer 5

• Impaired glucose tolerance of pregnancy is when the glucose rise level does not meet diagnostic criteria for gestational diabetes.
• The pregnant woman’s body undergoes changes to provide the best possible environment for the fetus.
  
  • Most of these happen naturally and well
  • but sometimes the mother is unable to make all of the necessary changes requiring help.
• GDM- the body is unable to adapt to the changing amounts of pregnancy hormones as the baby and placenta grow.
• Blood glucose level is raised above the normal ranges for pregnancy. GDM disappears in most women after delivery.
• ~8% of women will be affected by GDM.

Question 6

Conceptually, what is Gestational Daibetes Mellitus?

Answer 6

GDM- the body is unable to adapt to the changing amounts of pregnancy hormones as the baby and placenta grow.

Question 7

What are the screening reccomendations for Gestational Diabetes Mellitus in New Zealand?

Answer 7

All women should be offered a screening or diagnostic test for GDM during pregnancy (GDM can occur without identifiable risk factors).

1. Early Diagnostic testing @ Booking:
   
   • ​Booking Bloods: 12wks. HbA1c
   • Women who are at risk of having unrecognised glucose intolerance/diabetes at booking visit
2. Routine screening test: Women who are not at risk of diabetes
   
   • At 24-28weeks gestation
   • Screening test assesses the risk of patient.
   • Non fasting 50mg glucose/polycose given. Measure blood glucose level 1 hour after drinking.
3. Diagnostic Testing: OGTT (27weeks) offered if:
   
   • a) oral glucose tolerance test if positive screen test or
   • b) clinical high risk.
   • Overnight fasting, 75 g polycose load given. Measure venous blood glucose 1 and 2 hours after drinking.

Question 8

What is the WHO non-pregnant diagnostic criteria for Diabetes Mellitus?

Answer 8

fasting glucose > 7.0 mmol/L and/or

2 hour level >11.1 mmol/L

Question 9

What is the WHO non-pregnant diagnostic criteria for Impaired Glucose Tolerance?

Answer 9

fasting glucose <7.0mmol/L and the

2 hour level 7.8-11.1 mmol/L

Question 10

What is the diagnostic criteria for GDM in New Zealand?

Answer 10

HbA1c >50 mmol/mol (N = <41)

fasting >5.5mmol/L

2 hour level >9.0mmol/L

Question 11

What 4x main points should be covered when counselling a woman with T2DM, who wishes to become pregnant?

Answer 11

1. Emphasise on the benefits of glucose control
2. Advice on use of contraception until HbA1c is normal
   
   • to reduce risk of congenital abnormalities, still birth and other complications to fetus and mother.
3. Advice to take high dose folic acid (5 mg OD)
4. Discontinue: statins, ACEi or ARB.

Question 12

What are some risk factors for GDM or T2DM?

Answer 12

1. Previous GDM
2. Previous macrosomic baby (>4.5 Kg)
3. Ethnicity: Asian, Pacifica, Middle easter, Latin american, African, Maori
4. Fmhx: diabetes (2x 1st degree relatives)
5. Pmhx:
   
   • Age: >40 years
   • Obesity
   • PCOS
   • Glycosuria
6. Medications: Antipsychotic or prednisone
7. IVF pregnancy

Question 13

Why is the majority of screening for T2DM during 24-28weeks gestation?

Answer 13

• This is the period of pregnancy during which the baby is growing most rapidly and therefore the time when gestational diabetes is most likely to develop.
• Additionally, there is also enough time left for treatment to be effective.

Question 14

Why is HbA1c not an accurate measure for GDM?

Answer 14

1. snapshot/static measurement in time (120days)
   
   1. has a high false -ve rate
   2. therefore need to add on further tests
2. $$ expensive. Not cost effective.
3. Haemodilution effect
   
   1. cannot do HbA1c at 27weeks, due to haemodilution (decreased Hb during pregnancy). is an inaccurate result
   2. Also: havent studied appropriate ranges of HbA1c in pregnancy

Question 15

What are some maternal complications of GDM?

Answer 15

Increased risk of:

1. pre-eclampsia
2. prolonged labour –>
3. requiring IOL induction and c-section (macrosomic baby)
4. birth trauma
5. infection -esp. UTI
6. haemorrhage
7. postpartum:
   
   1. T2DM (50-80% risk. But risk is reduced with 12-18months of breast feeding)
   2. excess gestation weight gain
   3. Obesity
   4. CVD RF

Question 16

What are some fetal complications of GDM?

Answer 16

1. Congential abnormalities (only if pre-existing DM) (risk reduced if diabetic control)
   
   1. cardiac, neural tube, renal.
2. Macrosomia / Fetal Growth restriction
3. Still birth
4. Preterm birth
5. Organomegaly
6. Hyaline membrane disease
7. Unstable lie, malpresentation
8. Dystocia (esp. shoulder)
9. Polyhydramnios
10. Neonatal hypo: glycameia, calcaemia, magnesmia (early breastfeeding)
11. Neonatal polycythemia + Increased erythropoesis

NB: There is no direct increased risk of baby having diabetes as a result of GDM.

Question 17

What is macrosomia?

Answer 17

fetal hyperinsulinaemia

Question 18

What is the hypothesis for GDM causing stillbirth?

Answer 18

• unexplained fetal death possibly due to fetal hyper insulinemia which causes chronic hypoxia + lactic acidemia.
• A Macrosomic baby is more at risk of fetal demise/death, due to its increased O2 demands

Question 19

What is the management of GDM during pregnancy?

Answer 19

MULTI-DISCIPLINARY team approach (obstetrician, diabetes physician, diabetes educator, dietician, midwife and paediatrician).

• explain implications and discourage poor diabetic control

Treatment:

1. Conservative:
   
   1. Dietary therapy appropriate to maternal BMI and culture.
      
      • small, frequent meals. Composition: 200-220 carbs, 1/2 plate of non-starchy vegetables, 1/4 lean protein.
      • NB: Severe calorie restriction can predispose to ketonuria and infants that are small for gestational age.
   2. Moderate exercise
2. Pharmacological:
   
   1. Insulin therapy (consider if blood glucose goals are exceeded on >2 occasions within a 1-2 week interval, particularly in association with suspicion of macrosomia).
   2. Metformin

Monitoring/Management:

1. Monitor glycemic control (self)
2. Fetal growth scans (at 28, 36 weeks and as appropriate)

Delivery is determined using the 36-37weeks scan:

• Delivery 40+ wks: If normal growth (<90%) and no maternal issues
• Delivery 38-39wks: If abnormal growth and maternal symptoms

Question 20

What is the management of GDM during post-partum/following pregnancy?

Answer 20

All women who have GDM require:

1. OGTT 6 weeks/3months postpartum: to ensure their glucose tolerance has returned to normal.
2. 1 - 2 yearly screening for: diabetes and other cardiovascular risk factors.
3. OGTT every 1 - 3 years: depending on the result and women’s progress with lifestyle intervention.
   
   • In between, a fasting glucose and HbA1c may be adequate
4. Contraceptive advice: IUD best option

• Close follow up of children born to women with GDM for:
  
  • development of obesity
  • abnormalities of glucose tolerance.
    *

Question 21

Is there any followup for the child of a GDM mother?

Answer 21

Yes.

Following delivery, there is close follow up of a children born to women with GDM.

checking for:

• development of obesity
• abnormalities of glucose tolerance.

Question 22

How is timing of delivery determined if the mother has GDM?

Answer 22

Delivery is determined using the 36-37weeks scan:

• Delivery at 40+ wks: If normal growth (<90%) and no maternal issues
• Delivery 38-39wks: If abnormal growth and maternal symptoms

Question 23

What dietary advice is given to a mother with GDM?

Answer 23

• Small, frequent meals.
• Composed of: 200-220 carbs, 1/2 plate of non-starchy vegetables, 1/4 lean protein

NB: do not promote severe calorie restriction. Can predispose:

• ketonuria
• SGA infants

Question 24

Why is pres-existing DM worse than GDM?

Answer 24

1. Effect on baby:
   
   • organogenesis occurs at pre-coneption (<8weeks). Therefore increased risk of fetal anomalies and miscarriage, if poor glycaemic control during this period of fetal development
2. Worsen maternal comorbidities: (esp vascular)
   
   • Retinopathy: increased risk in pre-eclampsia and IUGR. often worsen during pregnancy
   • Take a retinal photography in Trimester

Therefore:

1. Early referral to DM clinic, to optimise BS levels <42mmolL-1 prior to conception
2. Contracpetion until BS optimised/well controlled
3. Folic acid 5mg

Question 25

What is the best form of contracpetion in a woman with a hx of GDM?

Answer 25

IUDs

• highly effective
• havent been associated with an increased infection risk
• Imperative that GDM mothers have a form of adequate contraception, starting 6-12weeks post-partum.
  
  • reduces the rate (50%) of unplanned pregnancies in woman with pmhx of GDM
  • Ensures adequate/optimal glycaemic control from the start of subsequent pregnancies

Question 26

Why is the Depo-Provera a sub-optimal contraceptive option for GDM mothers following pregnancy?

Answer 26

• associated with increased weight gain
• associated with glucose introlerance

Therefore: post-partum weightloss and maintanence of a healthy weight should be stressed, if they choose to go onto depo

Question 27

Why is COCP a suboptimal form of contraception for mother with pmhx of GDM?

Answer 27

• C/I in woman with DM and circulatory problems, due to the increased risk of thromboembolic disease (VTE)
• should not be given to a woman with elevate trigylceridses

NB: doesn’t seem to have significant effects on maternal glucose metabolism

Question 28

Why is POP a suboptimal form of contraception for mother with pmhx of GDM?

Answer 28

1. May increase LDL-C (+ reduced HDL-C). Therefore use of POP should be carefully considered in patients with Diabetes and Vascular disease
2. When a woman is breastfeeding she is deficient in E2
   
   1. mother already has stores of Progesterone. Therefore, if she takes POP (additional progesterone) –> these elevated levels of unopposed progesterone can increase levels of insulin resistance

Therefore, should consider:

• alternatives to POP OR
• Only short-term use of POP

However, if POP is the only contraceptive option for GDM mother, then contraception is better than an unplanned pregnancy.