Gestational Diabetes Mellitus (GDM)

Definition

Gestational diabetes mellitus (GDM) is defined as any degree of glucose intolerance with onset or first recognition during pregnancy (Metzger BE, 1998). Gestational diabetes occurs when pancreatic function is not sufficient to overcome the insulin resistance created by changes in diabetogenic hormones (estrogen, prolactin, human chorionic somatomammotropin, cortisol, and progesterone) during pregnancy.

Pathophysiology

The characteristic of GDM is increasing in insulin resistance. Insulin resistance is a normal phenomenon that present in the second trimester of pregnancy. Pregnancy hormones are thought to disrupt the action of insulin as binding to the insulin receptor. The disruption probably occurs at the level of the cell signalling pathway behind the insulin receptor. Since insulin promotes the entry of glucose into most of the cells, insulin resistance prevents glucose from entering the cells properly. As a result, glucose remains in the bloodstream, where glucose levels rise. More insulin injection is needed to overcome this resistance.

Risk Factor

·         A previous diagnosis of gestational diabetes or pre-diabetes, impaired glucose tolerance, or impaired fasting glycaemia

·         A family history revealing a first-degree relative with type 2 diabetes

·         Maternal age - a woman's risk factor increases as she gets older (especially for women over 35 years of age).

·         Ethnic background

·         Being overweight, obese or severely obese

·         A previous pregnancy which resulted in a child with a macrosomia (baby with large size)

·         Previous poor obstetric history

Complication

Mother

·         The risk largely related to uncontrolled high blood glucose levels and its consequences.

·         Increases with higher blood glucose levels.

·         Higher risk for congenital malformations (a defect that is present in birth).

·         Still unclear whether women with GDM have a higher risk of preeclampsia. (High blood pressure and excess protein in the urine after 20 weeks of pregnancy for women who previously had normal blood pressure.)

Baby

·         Growth abnormalities and chemical imbalances after birth, which may require admission to a neonatal intensive care unit.

·         Macrosomia in turn increases the risk of instrumental deliveries (e.g. forceps, ventouse and caesarean section) or problems during vaginal delivery.

                     

                     

Figure: forceps (left) and ventouse (right)

·         Increased risk of low blood glucose (hypoglycemia), jaundice (a condition with yellow color of the skin, mucus membranes, or eyes), high red blood cell mass (polycythemia) and low blood calcium (hypocalcemia) and magnesium (hypomagnesemia).

·         Not been clearly shown to be an independent risk factor for birth defects because birth defects usually originate sometime during the first trimester (before the 13th week) of pregnancy.