Diabetes mellitus in pregnancy

O24 .0-4/O24.9

This condition should ideally be managed in consultation with a specialist.

DESCRIPTION

Established diabetes: Diabetes (type 1 or 2) predating pregnancy.
Gestational diabetes (GDM): carbohydrate intolerance first recognised during pregnancy. It does not exclude the possibility that diabetes preceded the antecedent pregnancy .

Diagnostic criteria for GDM

Either a fasting plasma glucose ≥ 5.6 mmol/L OR a plasma glucose of ≥ 7.8 mmol/L two hours after a 75 g oral glucose tolerance test.

The following women should be screened for GDM, between 24 and 28 weeks of gestation:

  • Women of Indian ethnic origin.
  • BMI >35kg/m2.
  • Age > 40 years of age.
  • GDM in previous pregnancy.
  • Family history (first degree relative) of diabetes.
  • Previous unexplained third trimester fetal death.
  • Previous baby with birthweight >4 kg.
  • Polyhydramnios in index pregnancy.
  • Glycosuria (≥1+ glucose in urine).
  • A fetus that is large for gestational age.

GENERAL MEASURES

  • Stop smoking.
  • Moderate exercise.
  • Dietary advice.

Elective delivery at about 38 weeks’ gestation.

MEDICINE TREATMENT

The mainstay of therapy is insulin. An initial trial of metformin has a role in the following patients:

  • obese women, and
  • women with mild type 2 diabetes.

Even with careful selection, approximately half of patients will require addition of insulin for adequate glucose control.

LoEI [5]

  • Metformin, oral, 500 mg daily.
    • Increase dose to 500 mg 12 hourly after 7 days.
    • Titrate dose to a maximum of 850 mg 8 hourly according to glucose control.
    • Contra-indications to metformin: liver or renal impairment.
    • If not tolerated change to insulin.

Do capillary glucose profiles, i.e. pre-prandial and 1-hour and 2-hour post-prandial for breakfast, lunch and supper .
Aim for:

  • preprandial values < 5.3 mmol/L
  • 1-hour postprandial < 7.8 mmol/L
  • 2-hour postprandial < 6.4 mmol/L

LoEI [6]

Abnormal profiles

Diabetic women should be admitted for poor glucose control, despite metformin therapy.
Start insulin.
Insulin requirements may increase with increasing gestation and later readmission may be necessary.

Preferred insulin regimen

  • Insulin, short-acting with all 3 meals to maintain the postprandial levels .

AND

  • Insulin, intermediate-acting at bedtime (with a bedtime snack) to maintain preprandial levels.

Insulin dosing:

    • Total daily dose: 0.5 units/kg/day.
    • One third of the total dose: intermediate acting insulin at bedtime.
    • The remaining two thirds divided into three equal doses are given before each meal (breakfast, lunch and supper).

Adjust insulin dosage daily according to blood glucose profiles, until control is adequate.

Where the above recommended regimen is not feasible

Twice-daily regimen with biphasic insulin.

  • Insulin, biphasic.
    • Daily dose: 0.5 units/kg/day, two thirds, 30 minutes before breakfast and one third 30 minutes before supper.
    • Titrate to achieve target blood glucose as above.

LoEI [7]

Delivery:

Consider induction of labour at 38 weeks gestation, provided glucose control is adequate, or earlier with maternal co-morbid conditions, or if glycaemic control is poor. If the estimated fetal weight (EFW) on ultrasound is >4 kg, offer elective Caesarean delivery .

During labour:

Monitor serum glucose hourly.
Stop subcutaneous insulin.
Administer short acting insulin to maintain physiological blood glucose levels.

  • Insulin, short acting, continuous IV infusion, 20 units plus 20 mmol potassium chloride in 1 L dextrose 5% at an infusion rate of 50 mL/hour, i.e. 1 unit of insulin/hour.
    • If blood glucose < 4 mmol/L, discontinue insulin.
    • If >7 mmol/L, increase infusion rate to 100 mL/hour

Postpartum insulin requirements decrease rapidly.
During the first 48 hours give insulin 4-hourly according to blood glucose levels.
Resume pre-pregnancy insulin or oral hypoglycaemic regimen once eating a full diet.

The newborn is at risk of:

  • hypoglycaemia,
  • respiratory distress syndrome,
  • hyperbilirubinaemia,
  • congenital abnormalities.

Postpartum management

Contraception Z30.0 + (O24.3-4/O24.9)

Tubal ligation should be considered.
Consider:

  • Low-dose combined contraceptive in well-controlled cases.
  • Progestin-only preparation or intra-uterine contraceptive device if planning to breastfeed.

See PHC STGs and EML Family planning

Need for ongoing anti-diabetic therapy
Offer women diagnosed with GDM during the index pregnancy an oral glucose tolerance test after 6 weeks postpartum to assess whether they have diabetes needing ongoing therapy.

REFERRAL/CONSULTATION

  • Obese women,
  • Excessive fetal growth despite adequate diabetes control.
  • Poor glucose control despite adequate insulin.