Gestational Diabetes Melittus

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Definition of Gestational Diabetes Mellitus

The WHO has defined Diabetes Mellitus as either a raised fasting blood glucose level of > 7.8 mmol/L or a level of > 11.0 mmol/L 2 hours following a 75 g oral glucose load.

Pathogenesis of Gestational Diabetes Mellitus

Placenta secretes anti-insulin substances; such as human placental lactogen(HPL), hCG, estriol, cortisol and progesterone

Presence of these substances in the maternal blood.

Glucose intolerance develops in the mother; mainly if maternal β cells are unable to produce additional insulin which is required to counteract this antagonism

Maternal Gestational Diabetes Mellitus

Maternal nutrients mainly glucose can readily crosses placenta but not maternal insulin

As the mother develops hyperglycemia due to Gestational Diabetes Mellitushence fetal pancreas will secrete additional insulin to cope with the fetal hyperglycemia

Fetal β cells hyperplasia

Fetal hyperinsulinemia

Effects of Fetal Hyperinsulinemia

1. Reduced lung surfactant à Respiratory Distress Syndrome (RDS)

2. Increased erythropoiesis can leads to jaundice or hyperviscosity syndrome. Hyperviscosity syndrome will later develops into necrotizing colitis or renal vein thrombosis.

3. Increased fetal metabolism which will increases O2 demand. Low O2 supply from the mother can leads to intrauterine death.

4. Macrosomia à shoulder dystocia

5. Hypoglycaemia

6. Hypertrophic myocardiopathy

Effects of Diabetes on Pregnancy

1. Increased miscarriage rate

2. Increased perinatal loss due to intrauterine death (IUD)

3. Macrosomic baby hence is at risk of dystocia

4. Fetal lung maturation may be delayed; if the fetus was delivered prematurely, the risk of getting RDS is increased

5. Risk of preeclampsia

6. Risk of polyhydramnios

7. Susceptible to infections; mainly UTI and candida vaginitis

Gestational Diabetes Mellitus Pathophysiology by RN Speak on Scribd

Management of Diabetes

A. Pre pregnancy

The women who are known to be diabetic and women who have had gestational diabetes should seek medical attention before they get pregnant. This consultation offers opportunities in explaining to them about;

1. The reason for meticulously maintaining her blood glucose at normal level before conception

2. The need of taking folic acid to reduce the risk of neural tube defects

This consultation can also be used as an assessment for the presence of any complication related to diabetes, such as diabetic retinopathy and nephropathy. Women who are on oral hypoglycemic drugs should preferably be changed to insulin therapy. We should check for her glycosylated Hemoglobin, HbA1c that reflects her glucose control over the previous 10 weeks. High levels of HbA1c are associated with an increased rate of fetal abnormality.

B. Pregnancy

Euglycemic state should be maintained; with fasting glucose less than 5.3mmol/L and 2 hour post prandial blood glucose should be less than 6.7 mmol/L. Blood sugar profile should be checked before or after each meal; preprandial or postprandial glucose level and the result should be less than 6 mmol/L or 6.7mmol/L, respectively. Normal blood glucose level should be maintained with a mixture of short and medium-acting insulin. Ultrasound scan that was done during the first 12 weeks of pregnancy provides accurate estimation of the period of gestation. Meanwhile, scanning between 18– 20 weeks of gestation allows exclusion of any major malformations and around 34 weeks of gestation, it permits assessment of fetal growth. Regular assessment of fetal growth and wellbeing should be performed.

C. Timing of Delivery

Delivery at up to 40 weeks of gestation is possible if the sugar control is good. But if there is inadequate blood glucose control, or the presence of polyhydramnios, fetal macrosomia or maternal obesity delivery at 38 weeks of gestation is indicated. Delivery at earlier than 38 weeks is not really indicated to prevent Respiratory Distress Syndrome in the premature baby.

Management of Labour

The intention is to achieve vaginal delivery. Labour can be induced by doses of oxytocin. An artificial rupture of membrane (ARM) should be performed. Blood glucose level needs to be monitored at frequent intervals; mostly done at 2hourly. The fetus should be monitored throughout labour and during vaginal delivery shoulder dystocia should be anticipated. On the other hand, a caesarean section may be performed if there is significant petal macrosomia or poor fetal status (CTG), or if labour fails to progress satisfactorily. Uncomplicated diabetes not an indication for operative delivery.

Follow Up of Women Who Have Had Gestational Diabetes Mellitus

Follow up is important as up to 50% of women with Gestational Diabetes Mellitus may develop overt diabetes; mainly Type II. At the follow up visits, we should encourage her to follow a diet which is appropriate for a diabetic. She should also be advised to take these following measures;

1. Avoid becoming obese

2. Take regular exercises

3. Avoid cigarette smoking

4. Checked annually for hypertension

These women have a 50% chance of developing Gestational Diabetes Mellitus in the future pregnancy. If she intend to become pregnant again, testing for hyperglycaemia before conception or in early pregnancy is recommended.