This condition should ideally be managed by a specialist.

DESCRIPTION

Established diabetes: Diabetes (type 1 or 2) predating pregnancy.

Gestational diabetes: any degree of carbohydrate intolerance first recognised during pregnancy. It does not exclude the possibility that diabetes preceded the antecedent pregnancy.

Diagnosis of gestational diabetes mellitus

Screen women with the following:

• Glycosuria 1+ on 2 occasions, or 2+ on one occasion.
• Family history of diabetes. o     Previous gestational diabetes.
• Weight > 100 kg or BMI > 40 kg/m².
• Previous unexplained stillbirth.

Previous macrosomic baby (weight > 4 000 g).

• Age > 40 years

• Polycystic ovarian syndrome.
•     Acanthosis nigricans. o     Polyhydramnios in current pregnancy.

Diagnostic criteria

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.

GENERAL MEASURES

Diet

Diabetic diet of not less than 7 200 kilojoules (1 800 Kcal) unless grossly obese. »     protein 15%,

»     fat 25% ,

»     high fibre carbohydrate 60%.

Eat 3 meals and 3–4 snacks/day.

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 type 2 diabetes.

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

•     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 six-point blood glucose profiles, i.e. pre- and 1 hour post-breakfast, lunch and supper.

Normal profiles (adequate control)

Preprandial levels < 6 mmol/L and 1 hour postprandial < 7.8 mmol/L, repeat the profiles 2-weekly until 34 weeks and then weekly until delivery.

Abnormal profiles

Start insulin.

Diabetic women should be admitted initially for good control.

When adequate glucose monitoring can be maintained during pregnancy, e.g. home blood glucose monitoring with consultation or long-term admission, the following levels should be aimed for:

»     preprandial levels:     < 6 mmol/L

»     1-hour postprandial:     < 7.8 mmol/L

Insulin requirements may increase with increasing gestation and later readmission may be necessary.

Preferred regimen

Use intermediate acting insulin between 21:00 and 22:00 to maintain preprandial levels and short acting insulin with all 3 meals to maintain the post prandial levels.

Starting dose may be based on previous insulin requirements, if known, or empiric starting dose:

• Insulin, intermediate acting, 10 units.
• Insulin, soluble, short acting, 5 units 30 minutes before main meal. 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.

Empiric starting dose if previous insulin requirements are not known:

• Insulin, biphasic.

  o Daily dose: 0.2 units/kg/day, two-thirds of the dose 30 minutes before breakfast and one-third 30 minutes before supper. o Titrate daily to achieve target blood glucose as above.

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 o If blood glucose < 4 mmol/L, discontinue insulin. o If > 9 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 prepregnancy insulin or oral hypoglycaemic regimen once eating a full diet.

The newborn is at risk of:

»     hypoglycaemia,

»     respiratory distress syndrome, »     hyperbilirubinaemia, and »     congenital abnormalities.

Postpartum contraception

Tubal ligation should be considered.

Consider:

o     Low-dose combined contraceptive in well-controlled cases. o     Progestogen-only preparation or intra-uterine contraceptive device if blood glucose control is poor.

REFERRAL/CONSULTATION

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p style=”margin-left: 54pt”>»     Blood glucose not adequately controlled on diet alone.