Diabetes Mellitus in Pregnancy

Introduction

Diabetes Mellitus in pregnancy includes individuals known to be diabetic prior to pregnancy and those who develop impaired glucose tolerance during pregnancy.
Gestational diabetes refers to impaired glucose tolerance of any degree that develops or is first recognized during the current pregnancy, irrespective of whether it resolves after delivery or not.
Diabetes is associated with poor health outcomes for a mother and her baby if not properly managed.
Many patients with gestational diabetes are asymptomatic making screening for all pregnant women mandatory to identify those at risk.
A fasting blood glucose test must be done on all pregnant women at booking and also at 28-32 weeks (SeeĀ  ‘Antenatal Care’).
The management of diabetes mellitus in pregnancy and the puerperium involves close monitoring of the woman by a multidisciplinary approach comprising a team of obstetricians, midwives, nurses, dieticians, physicians, anaesthetists and paediatricians.
Labour (induced or spontaneous) and Caesarean section are best supervised in hospital under specialist care.
Anti-diabetic treatment requirements reduce dramatically after delivery hence, post delivery treatment doses must be tailored to each individual patient’s needs.
The newborn baby of a diabetic mother needs special care and is best managed by a paediatrician/ neonatologist.
Hypoglycaemia in the baby in the first few hours of birth is a major problem.
It can be prevented by initiating early (within 1 hour) breastfeeding.
They may also require management for respiratory distress syndrome, electrolyte imbalances (e.g. hypercalcaemia, hypokalaemia, hypomagnesaemia) and hyperbilirubinaemia.
All diabetic mothers must be counselled on family planning.

Causes of diabetic mellitus in pregnancy

  • Pre-existing Type 1 diabetes mellitus
  • Pre-existing Type 2 diabetes mellitus.
  • Gestational diabetes mellitus

Symptoms of diabetes mellitus in pregnancy

  1. Usually asymptomatic
  2. Previous history of large babies (>4 kg)
  3. Previous poor obstetric history (foetal deaths, miscarriages etc.)
  4. Other features of diabetes (See ‘Diabetes Mellitus’)

Signs of diabetes mellitus in pregnancy

The signs of diabetes mellitus in pregnancy include the following:

  1. Foetus larger than gestational age (as assessed by serial symphysio fundal height or by ultrasound scan)
  2. Foetus smaller than gestational age (IUGR)
  3. Presence of polyhydramnios
  4. Other signs of diabetic complications (See ‘Diabetes Mellitus’)

Investigations

  • All basic Antenatal Care Investigations
  • Ultrasound scan
  • Foetal anomaly scan at 16-22 weeks Serial scans for growth assessment in third trimester
  • Urine culture and sensitivity (monthly)
  • High vaginal swab for candidiasis
  • Blood urea, electrolytes and creatinine
  • Blood glucose profile (Fasting blood glucose and 2-hour post prandial blood glucose monthly in the lab; more frequently by self monitoring)
  • Glycated haemoglobin (HbA1C) every 6-8 weeks

Note

There is no place for urine glucose estimation in the management of diabetes in pregnancy except for screening.
Self-monitoring of blood sugar should be encouraged for those who can afford a glucose meter.

Treatment for diabetes mellitus in pregnancy

Treatment objectives

The treatment objectives of diabetes mellitus in pregnancy are:

  1. To achieve normal blood glucose and glycated haemoglobin levels throughout pregnancy, labour, delivery and puerperium
  2. To prevent maternal and foetal complications
  3. To prevent neonatal morbidity and mortality
  4. To detect and manage other associated complications e.g. preeclampsia

Non-pharmacological treatment

  1. General measures (dietary modification, exercise, patient counselling and education, blood glucose monitoring must be discussed with a dietician, obstetrician or midwife, respectively)
  2. Frequent ANC visits are required
  3. Delivery
    1. by 40 weeks gestation: in well controlled patients with no complications
    2. by 38 weeks gestation; in Insulin treated patients and those with complications
  4. Caesarean section; for patients with either of the following;
    • severe pre-eclampsia, previous caesarean section, advanced maternal age, malpresentation or foetal macrosomia
  5. If elective preterm delivery is necessary, mature the foetal lungs with corticosteroids under specialist care
  6. Puerperium
    • Close blood glucose monitoring in the first 48 hours after delivery

Pharmacological treatment

Notes on glycaemic control of diabetes in pregnancy

Before planned pregnancy

  • Optimise glycaemic control in known diabetics before pregnancy.

During pregnancy

  • If diet alone cannot control the blood glucose level consider hypoglycaemic agents: metformin, glibenclamide and insulin
  • Diabetic patients on oral medication who become pregnant can be maintained on their oral medication if sugar control is satisfactory (fasting glucose levels between 4-6 mmol/L and 2-hour postprandial glucose between 4-7 mmol/L; glycated Hb [HbA1c] less than 6.5%)

Indications for oral antidiabetic agents use:

  • Gestational Diabetics who fail to achieve satisfactory control with diet and exercise alone (FBS > 6.1mmmol/l)
  • Poor compliance to insulin e.g. poor administration skills
  • Poor glycaemic self monitoring
  • Insulin therapy poses financial burden or is not readily available

Absolute Indications for Insulin use

  • Signifiant diabetic related morbidity exists e.g. nephropathy, retininopathy, neuropathy
  • Persistently high Haemoglobin Alc
  • Persistent ketonuria
  • Significant obstetric morbidities e.g. IUGR, polyhydraminios, foetal macrosomia,
  • During antenatal corticosteroid therapy with expected deterioration of glycaemic control
  • Poor glycaemic control with oral antidiabetic agents

Evidence Rating: [B]
Metformin, oral,

  • 500 mg 8-12 hourly. (max. dose 2g per day)

And/Or

Glibenclamide, oral,

  • 2.5-5 mg 12-24 hourly.
  • Increase dose by 5 mg if necessary until max. dose of 15 mg/day

Note

Metformin can be given as monotherapy or in combination with insulin and/or Sulphonylurea
The use of sulphonylureas (e.g. glibenclamide) in pregnancy should generally be avoided because of the risk of neonatal hypoglycaemia.
However, glibenclamide can be used in the 2nd and 3rd trimester in women with gestational diabetes.

And/Or

Insulin
Evidence Rating: [A]
(See Insulin Therapy in ‘Diabetes Mellitus’)

  • Start with small doses (e.g. total daily dose of 6-10 units) of NPH insulin or premixed insulin (which has 30% of regular and 70% of NPH insulin), subcutaneously.
  • Give approximately two-thirds of the total daily dose before breakfast and one-third before dinner.
  • Adjust the insulin doses before breakfast and/or dinner by plus or minus 2 units according to results of blood glucose tests.
  • Monitor insulin therapy with 2-4 weekly FBS (and 2-hour post prandial blood glucose where possible) up to 34 weeks then weekly till delivery.
  • Keep fasting glucose levels between 4-6 mmol/L and 2-hour postprandial glucose between 4-7 mmol/L. This is often achievable on an out-patient basis. However, some patients would need to be admitted to hospital for short periods to ensure good glycaemic control.
  • Insulin requirements during labour should be given according to a sliding scale (SeeĀ  ‘Diabetic ketoacidosis‘)
  • Insulin requirements during caesarean section and other operative procedures (using a sliding scale or Glucose-Potassium-Insulin infusion or GKI) should be discussed with the anaesthetist

Referral Criteria

Refer to hospital for specialist care.
For the convenience of patients
shared care between specialist and medical officer may be appropriate.