8.3 Gestational Diabetes

Question 1

what is the definition of gestational diabetes?

Answer 1

Gestational diabetes mellitus (GDM) is a pregnancy-specific condition defined as hyperglycaemia recognised for the first time in the 2nd/3rd trimester of pregnancy:

Question 2

In normal pregnancy, there is a balance between increased insulin resistance and increased insulin release which helps to maintain normal glycaemia.

Placenta releases various hormones (_______________) which antagonise insulin effects → decreases sensitivity to insulin (less uptake of excess glucose):
• Insulin resistance increases 3-fold in the _____________ and rises to peak resistance in the ________________ (rise in feto-placental factors further decreases maternal insulin sensitivity)
• Serves as an effective adaptive mechanism to pregnancy: stimulates maternal use of alternate energy sources rather than glucose → frees glucose for foetal use
• After placental delivery, reduced placental hormones restores insulin sensitivity and blood glucose levels back to normal

Insulin release: Increased maternal oestrogen and progesterone in pregnancy stimulates ________________ → increased insulin release:
• Helps to maintain glucose levels (even as insulin resistance increases during pregnancy)
• Insulin promotes glucose metabolism throughout the body

Answer 2

hPL/hCS, progesterone, cortisol, hCG, oestrogen;

2nd trimester;

late 3rd trimester;

pancreatic β cell hyperplasia

Question 3

What are the risk factors for the development of GDM?

Answer 3

• Obesity: BMI > 30 kg/m2 (already increased insulin resistance)
• Ethnicity: South Asian, Black Caribbean, Middle Eastern
• Previous history of GDM or large baby > 4.5kg or prior stillbirth
• Family history of diabetes (in 1st degree relatives)

Question 4

What is the management of GDM?

Answer 4

At-risk women (identified based on risk factors) should be offered education and screening:
• Women with risk factors should be informed that in most women with GDM, changes in diet and increase in exercise are effective in reducing plasma glucose levels
• Only 10 – 20% of women need medical intervention (metformin/insulin)
• Teach self-monitoring/recording of glucose level at home (using target blood glucose level as per local protocol)
• If GDM is not detected/controlled, there is a risk of adverse pregnancy outcome
• Diagnosis associated with increased monitoring/intervention in pregnancy/labou

Question 5

What is the acute foetal complications of GDM?

Answer 5

1. Foetal macrosomia (due to increased glucose supply)
2. Polyhydramnios (increased amniotic fluid; due to foetal polyuria from hyperglycaemia → foetal urine is an important source of amniotic fluid)
3. Preterm birth & unexplained foetal death
4. Trauma associated with difficult delivery (foetus too big)

Question 6

What is the acute neonatal complications of GDM?

Answer 6

1. Hypoglycaemia (neonates born to mothers with GDM must have their glucose levels monitored closely in the early neonatal period) → early feeding helps to reduce the risk
2. Hypomagnesaemia & hypocalcaemia (due to increased HbA1c affecting the foetal thyroid glands) → corrects itself over time
3. Polycythaemia (due to increased growth hormone) → increased lysis of RBCs as compensatory response → increased release of bilirubin → foetal liver not mature enough to conjugate and excrete it → hyperbilirubinaemia and neonatal jaundice
4. Hypercardiomyopathy
5. Respiratory distress syndrome (type II pneumocytes slower to mature)

Question 7

What is the acute maternal complications of GDM?

Answer 7

1. Elevated incidence of pre-eclampsia (HTN + proteinuria)
2. Obstructed labour (due to large foetal size)
3. Birth trauma/difficult operative delivery (also due to large foetal size)
4. Infections (due to increased blood glucose levels)

Question 8

what are the long term complications of GDM?

Answer 8

1. Higher maternal risk of developing T2DM later in life (~10% of women with GDM are diagnosed with DM soon after diabetes; 20 – 60% risk of developing diabetes within 5 – 10 years of index pregnancy)
2. Likelihood of recurrence of GDM in future pregnancies (30 – 84%) → 75% require insulin; GDM develops early in pregnancy 3. Higher offspring risk of developing childhood obesity and T2DM

Question 9

What tests are used to screen/ diagnose GDM?

Answer 9

• Fasting plasma glucose (Patients are asked not to eat/drink anything (except water) for 8 – 10 hours before their blood glucose level is taken)
• Glucose challenge test (Patient drinks a 50g glucose solution then blood glucose level is
  taken 1 hour later)
• oral glucose tolerance test –> One-step: 75g 2-hour OGTT (blood taken at 1-hour & 2-hour marks)

Question 10

GDM resolves shortly after delivery for most women → those with persistent glucose intolerance are likely to have underlying diabetes (not of gestational origin):
• Women with GDM have a 7-fold increased risk of develop T2DM compared to those with normoglycaemic pregnancy
• At 6 – 12 weeks postpartum: only 1/3 of women with persistent glucose intolerance have abnormal fasting blood glucose level → ___________ recommended
• NICE recommendations: fasting glucose at 6 – 13 weeks postpartum to exclude diabetes rather than routinely offering 75g OGTT → risk of missing out diabetics (but FPG is more cost effective and easy to do as a screening tool)
• Tests are conducted at least 6 weeks postpartum because all the changes that occur during pregnancy are reversed during the 6-week period

Answer 10

75g fasting 2-hour OGTT