GESTATIONAL
DIABETES
By Stephanie See
INTRODUCTION
“ Any hyperglycaemia with first onset or presentation during pregnancy.
WHAT ARE THE NUMBERS?
Of 700,000 women that give birth each year, 5%
have pre-existing diabetes or gestational diabetes.
87.5% of these women develop gestational diabetes
Prevalence of T1DM and T2DM increasing
Incidence of GDM increasing due to higher rates of
obesity and pregnancy in older women.
Common in Asians, Middle East and Black Africans.
RISK FACTORS
 BMI above 30
 Previous macrosomic baby
weighing 4.5kg or above
 Previous gestational diabetes
 Family history of diabetes
 Minority ethnic origin with high
prevalence of diabetes
 >35 years old
 Smoking
40% of mothers with GDM have no risk factors and are asymptomatic,
hence screening is made available to all expectant mothers.
PATHOPHYSIOLOGY
❶ This is due to HUMAN PLACENTAL LACTOGEN (HPL)
Produced by the synctiotrophoblast (nutritional
barrier). This hormone causes:
↓ maternal Insulin sensitivity
↓ maternal glucose utilization
↑ Lipolysis
❷ STEROID HORMONES, Corticosteroids &
Progesterone, especially when raised during
pregnancy have an anti-insulin effect.
❸ Some insulin may be destroyed by the PLACENTA
Demand for insulin will increase by ~30%.
If the pancreas cannot keep up, it will lead
to higher than normal BM  GDM
Baby’s Risks
Complication
Reason
LGA/Foetal Macrosomia
(Abdo Circ >90th centile)
Due to the ↑ glucose provided to the foetus, it will grow larger than usual
 shoulder dystocia during natural birth.
3x ↑ Risk of Congenital
Malformations- CNS & CVS
Suggested (but not proven) that hyperglycaemic environments are
teratogenic. However, GDM usually presents later in the pregnancy.
Respiratory Distress
Syndrome
Insulin ↓ pulmonary phospholipid production  surfactant ↓  surface
tension ↑ hence crucial when the baby starts breathing post-partum.
Postpartum neonatal
hypoglycaemia
Foetus experiences chronic hyperinsulinaemia in-utero. Due to low glucose
after birth  hypoglycaemia. Given IV glucose/direct feeding
Neonatal jaundice
Insulin is thought to stimulate growth of erythroid colonies, hence ↑ levels of
erythropoiesis  polycythaemia  ↑ breakdown of RBC  ↑ bilirubin in
the foetal blood  neonatal jaundice. Treated by placing baby under UV
light to break down the bilirubin under the skin.
The baby is also at a higher risk of developing T2DM and obesity as it grows older.
Mother’s Risks
Complication
Reason
Increased risk of tears
Due to shoulder dystocia during natural birth. Hence GDM mothers
usually deliver at 37-38 weeks on treatment or schedule a C-section
before 40 weeks and 6 days.
Polyhydramnios
Due to foetus’ increased urinary frequency in the amniotic sac
(amniotic fluid mainly consists of urine)
Increased risk of Stillbirth, Preterm Labour and Miscarriage
Increased risk of Type II Diabetes
INVESTIGATION
DIAGNOSIS
WHEN?
• For women with risk factors, test at 24-28 wks
• For women with history of GDM, test immediately
and at 24-28 weeks if first results are normal.
• If glycosuria detected during antenatal testing (>2
on 1 occasion or >1 on 2+ occasions)
HOW?
• 2-hour 75g oral glucose tolerance test (OGTT)
Fast 8-14hrs
overnight
75g glucose
given at start of
test
Blood glucose
measured at the
start and
intervals
Fasting plasma glucose level of
5.6mmol/litre or above
OR
2-hour plasma glucose level of
7.8mmol/litre or above
CLASSIFICATION
A1
A2
Abnormal OGTT
Normal fasting and
2hr post-prandial
Abnormal OGTT
Abnormal fasting and
2hr post-prandial
Diet and exercise
Pharmacological
Intervention
TREATMENT AND MANAGEMENT
Target glucose levels during pregnancy: 5.3 (Fasting), <7.8 1hr postprandial, <6.4 2hr postprandial
During labour: Glucose monitored every hour and kept between 4-7 mmol/L
After birth: Stop treatments. Feeding of baby encouraged.
Conservative Exercise
Low-impact activities, especially after meals (Walking, Swimming, Yoga)
Diet
Regular balanced diet that is nutritionally complete (with more fruits &
vege)
Complex Carbohydrates may be useful = Low GI foods
Avoid food labelled ‘diabetic’ or ‘suitable for diabetics’
Recommend oily fish, lean meat and polyunsaturated fats
Medical
If A2 GDM or conservative management ineffective for 1-2 weeks, consider:
• Metformin +/- Insulin
• Glibenclamide if metformin is not tolerated and insulin declined.
*No other oral treatments can be used during pregnancy.
SYSTEMATIC REVIEW OF PHARMACOLOGICAL TREATMENTS
Balsells, M., Garcia-Patterson, A., Sola, I., Roque, M., Gich, I. and Corcoy, R. (2015). Glibenclamide, metformin, and insulin for
the treatment of gestational diabetes: a systematic review and meta-analysis. BMJ, 350(jan21 14), pp.h102-h102.
Study Objective: To evaluate the short-term outcomes of Glibenclamide, Metformin and Insulin for
treating women with GDM. Only RCTs were included in the selection criteria.
Glibenclamide vs Insulin
In Glibenclamide group, birth weight was 100g higher, and neonatal
hypoglycaemia and Macrosomia incidence is 2x higher
Metformin vs Insulin
Metformin had better outcomes with maternal weight gain, postprandial
glucose and hypertension, but worse foetal outcomes and more side effects.
Metformin vs
Glibenclamide
Metformin had overall better outcomes, but had higher average treatment
failure.
Conclusion: Insulin and Metformin is more effective in reducing complications compared to
Glibenclamide. Metformin (plus insulin when required) performs better than insulin. Hence the current
guidelines are appropriate in recommending Metformin and Insulin over Glibenclamide.
However, another systematic review by Brown et al, 2017 have shown no differences in effectiveness
between the oral pharmacological therapies.
MONITORING OF DIABETIC COMPLICATIONS
FOR BABY: Regular foetal USS (18-20 weeks)
FOR MOTHER:
Risk Factor
Management
Pre-eclampsia/ Labetolol, Methyldopa, Methynifedipine
Hypertension
ACE-i and angiotensin-II antagonists should not be used, due to increased risk
of congenital abnormalities (foetal renal damage)
Retinopathy
Retinal Digital Screening, with mydriasis using tropicamide. When?
• At the beginning of pregnancy, 16-20 wks if +ve result and 28 wks if -ve
Nephropathy
Renal Screening. Refer to nephrologist if:
• Serum Creatinine (>120)
• Urine Dipstick- Albumin: Creatinine >30mg/mmol or protein >2g/day
BREAST-FEEDING AND GLYCAEMIC CONTROL
In women with insulin-treated pre-existing Type 1 diabetes:
 Insulin should be immediately reduced after birth
 Blood glucose levels must be monitored carefully
 Must explain that they are at a higher risk of hypoglycaemia post-partum, especially
when breast-feeding. Hence, they are advised to eat before or during feeds.
In women with pre-existing Type 2 diabetes:
 Can resume metformin or Glibenclamide post-partum but other oral hypoglycaemic
agents should be avoided while breast-feeding.
In women who developed gestational diabetes during pregnancy:
 Must discontinue hypoglycaemic treatment immediately after birth
SUMMARY
TO MAKE AN INFORMED DECISION, EXPLAIN THAT:
1. In some, gestational diabetes will respond to changes in diet and exercise
2. Majority of women will need oral blood glucose-lowering agents or insulin therapy
if conservative management is ineffective.
3. If gestational diabetes is not detected and controlled, there is a small increased
risk of serious adverse birth complications such as shoulder dystocia
4. A diagnosis of gestational diabetes will lead to increased monitoring, and may
lead to increased interventions, during both pregnancy and labour.
REFERENCES
• NICE UK (2018). Diabetes in pregnancy: management from preconception to the postnatal
period | Guidance and guidelines | NICE. [online] Available at:
https://www.nice.org.uk/guidance/ng3/chapter/1-Recommendations#gestationaldiabetes-2 [Accessed 11 Mar. 2018].
• Diabetes UK. Recommendations for the management of pregnant women with diabetes
(including gestational diabetes). 2003
• Brown, J., Martis, R., Hughes, B., Rowan, J. and Crowther, C. (2017). Oral anti-diabetic
pharmacological therapies for the treatment of women with gestational
diabetes. Cochrane Database of Systematic Reviews.
• Balsells, M., Garcia-Patterson, A., Sola, I., Roque, M., Gich, I. and Corcoy, R. (2015).
Glibenclamide, metformin, and insulin for the treatment of gestational diabetes: a
systematic review and meta-analysis. BMJ, 350(jan21 14), pp.h102-h102.
• DVLA (March 2015). For Medical Practitioners. At a glance guide to the medical standards
for fitness to drive.