Gestational Diabetes Flashcards
Definition of gestational diabetes
A condition in which women without pre-existing diabetes exhibit high blood glucose levels during pregnancy. It is caused by reduced insulin sensitivity and generally resolves after birth.
What is the aetiology of GDM
- Normal pregnancy is characterised by progressive insulin resistance and pancreatic beta cell hyperplasia (secondary to effects of human placental lactogen)
- GDM develops where insulin resistance overcomes pancreatic beta cell ability to maintain normoglycaemia
- Resistance usually starts to develop in the 2nd trimester and peaks in the 3rd trimester- allows for steady glucose supply to the foetus
- After delivery, hPL is no longer produced meaning pregnancy-associated insulin resistance disappears normoglycemia
What is the major consequence of GDM
Foetal MACROSOMIA, inhibited surfactant production (impaired lung function), increased oxygen consumption due to elevated metabolic rate (can cause foetal hypoxia and metabolic acidosis), increased erythropoiesis and polycythaemia
Risk factors of GDM
- BMI above 30 kg/m2
- Previous macrosomic baby weighing more than 4.5Kg
- Previous GDM
- FHx of diabetes (first-degree relative with diabetes)
- An ethnicity with a high prevalence of diabetes (black Afro-Caribbean, middle eastern, South Asian)
WHo should be screened for GDM
Anyone with risk factors should be screened with an oral glucose tolerance test at 24-28 weeks of gestation. Women with previous GDM should also have an OGTT soon after their booking visit.
Incidence of GDM
1-5 in 100 women develop GDM in pregnancy
Complications of GDM
The most significant immediate complications of GDM are large for dates foetus and macrosomia (generally accepted as foetal weight >4000g), associated with:
* Increased birthweight
* 10% preterm labour
* Polyhydramnios due to macrosomia
* Shoulder dystocia and birth trauma
* Foetal compromise, foetal distress and sudden foetal death are more common and related to poor control in the third trimester
* CS or instrumental delivery are more common due to foetal compromise and increased foetal size
Longer-term, women are at a 10x increased risk of developing T2DM after pregnancy:
* UTI, wound and endometrial infection are more common
* Pre-existing HTN found in 25% of overt diabetics
* PET is more common
Investigations for GDM
- The 75g 2hr OGTT should be conducted in any woman with risk factors for GDM
For women who have had GDM in a previous pregnancy, offer:
* Early self-monitoring of BG or
* A 75g 2hr OGTT as soon as possible after booking (whether in first or second trimester) and a further 75g 2hr OGTT at 24-28 weeks if the results are normal
* Consider further testing to exclude GDM in women who have the following reagent strip tests during routine antenatal care:
* Glycosuria of 2+ or above on 1 occasion
* Glycosuria of 1+ or above on 2 or more occasions
* May also consider further testing if there is evidence of polyhydramnios or large for dates foetus
GDM can be diagnosed if the woman has either:
* A FBG of 5.6 mmol/L or above
* A 2-hour plasma glucose of 7.8 mmol/L or above
* Women who are diagnosed should be offered a review with the joint diabetes and antenatal care clinic within 1 week. Their primary healthcare team should also be informed
* Offer all pregnant women with diabetes USS monitoring of foetal growth and amniotic fluid volume every 4 weeks from 28 to 36 weeks
* (Foetal wellbeing monitoring is not indicated before 36 weeks unless there is risk of FGR)
Where are women with GDM managed
- Patients are managed in the ‘joint diabetes and antenatal clinic (after review within 1 week, women should be in contact with the clinic **every 1 to 2 weeks **throughout pregnancy)
How should women with GDM be advised
- That good BG control throughout pregnancy will reduce the risk of foetal macrosomia, trauma during birth, induction of labour, neonatal hypoglycaemia and perinatal death
- That their care will be jointly managed by the doctors and midwives
- That treatment includes diet and exercise modification, and could involve medications
- To maintain their CGB below the following target levels, if these are achievable without causing problematic hypoglycaemia:
o Fasting: 5.3 mmol/litre
o 1 hour after meals: 7.8 mmol/litre OR 2 hours after meals: 6.4 mmol/litre. - To eat a healthy diet during pregnancy, and switch from high to low glycaemic food
- Refer all women to a dietician and advise to exercise regularly (walking for 30 minutes after a meal)
How should women be managed if glucose targets are not met with diet and exercise alone
- If blood glucose targets are not met with diet and exercise changes within 1 to 2 weeks, offer metformin (can offer insulin if metformin contraindicated)
- If targets remain unmet, offer concomitant insulin
- Glibenclamide (a sulfonylurea) is suggested as an option for women who decline insulin or cannot tolerate metformin.
Management of severe GDM
For women with GDM with FBG levels> 7.0 mmol/L OR between 6.0-6.9 AND complications such as macrosomia and polyhydramnios, consider:
* Immediate treatment with insulin, with or without metformin AND diet and exercise modification
* Consider rapid-acting insulin analogues (there is impaired awareness of hypoglycaemia in pregnancy)
* Should always have a fast-acting form of glucose available
When should women with GDM test their BG
- Advise pregnant women with GDM who are on a multiple daily insulin injection regimen to test their fasting, pre‑meal, 1‑hour post‑meal and bedtime blood glucose levels daily
- Advise women with GDM to test their fasting and 1hr post-meal BG levels daily if they are managing with diet and exercise changes alone or oral therapy
When should women with GDM be referred to a nephrologist
Consider referral to a nephrologist If (do not use eGFR as a measure of kidney function):
* Serum Cr is 120 micromol/L or more
* Urinary albumin: creatinine ratio is greater than 30 mg/mmol
* Total protein excretion exceeds 0.5 g/day
How does GDM affect steroid and tocolysis use
- Diabetes should not be considered a contraindication to tocolysis or to antenatal steroids for foetal lung maturation-> women with insulin‑treated diabetes who are taking steroids for foetal lung maturation, give additional insulin and monitor closely