Gestational diabetes mellitus (GDM) is defined as any glucose intolerance, which appears and is first diagnosed during pregnancy in a woman who was previously never diabetic. It is diabetes seen only in pregnancy. It is, therefore, also called diabetes during pregnancy.

It is characterized by high blood sugar levels, which are first seen in a woman during her pregnancy. It is more commonly seen during the last three months (3rd trimester).Gestational Diabetes Symptoms and Signs during Pregnancy

The criteria for a woman to be diagnosed with gestational diabetes are when glucose intolerance continues beyond 24–28 weeks of gestation.

It is mostly detected through prenatal screening because, in most pregnant women, symptoms are absent. It can, however, be treated.

The vast majority of such cases end with a healthy baby but GDM does pose health risks to the mother and the baby.

After delivery, however, the blood sugar of the mother returns to its normal limits but gestational diabetes is a warning sign that you could develop diabetes type 2 later on in life.

And your risk increases by 66% of developing gestational diabetes in subsequent pregnancies. However, following certain lifestyle measures and proper eating habits, significantly reduce this risk.

Statistics: Worldwide and US

GDM is the most common metabolic complication of pregnancy.  It is most commonly seen between the ages of 19 to 40 years.

The prevalence of GDM varies worldwide, depending on the population and the human race. Its prevalence is higher in Asian, Latin-American, and Indian women.

The International Diabetes Federation estimates that 16% of babies born worldwide in 2013 had complications due to GDM.

According to the Centers for Disease Control and Prevention, the estimated prevalence of gestational diabetes mellitus (GDM) in the United States may be as high as 9.2%. It could even be as high as 14% – that is roughly 200,000 cases annually in the United States.

GDM prevalence increased with maternal age and the number of previous children and decreased with higher maternal education.

As the incidence of type 2 diabetes has increased, so have the numbers of GDM.

In India, more than one million cases are detected every year.


The exact pathophysiology of gestational diabetes is still not clear.

During early pregnancy, the increasing levels of estrogen, progestin, and other pregnancy hormones lead to decreased blood glucose levels, increased fat deposits, delayed gastric emptying, and an increase in appetite.

The underlying pathology is the insulin resistance of the body cells, which do not respond to insulin. The pregnancy hormones are thought to be responsible for this probably because they interfere with cell signaling pathways.

Due to insulin resistance, the cells in the skeletal muscle and fat tissue do not take up the glucose from the bloodstream and therefore, blood glucose levels remain high.

The body produces more insulin to combat the increased glucose levels, but this compensatory measure does not work due to cellular resistance to insulin.

In GDM, insulin production can be 1.5 to 3 times more than that seen in a normal pregnancy.

Healthy blood sugar levels range

For pregnant women without diabetes:

  • average fasting glucose levels vary between 69 mg/dL and 75 mg/dL
  • one hour after eating, they range from 105 mg/dL to 108 mg/dL

According to the 2014 American Diabetes Association practice guidelines. for pregnant women with gestational diabetes or pre-existing diabetes:

  • fasting sugar should be less than 95 mg/dL
  • one hour after eating, blood sugar should be less than 140 mg/dL
  • two hours after eating, blood glucose levels should be less than 120 mg/dL

What Causes Gestation Diabetes? Etiology

In gestational diabetes mellitus, the oral glucose tolerance test (OGTT) gut absorption is significantly low. Thus, these high glucose levels of pregnancy do not result from rapid or increased glucose absorption from the gut.

The etiology of GDM is very simple. As with diabetes mellitus type 1 and 2, women with gestational diabetes suffer from glucose intolerance wherein instead of glucose being taken up by the body cells to produce energy, it stays accumulating in the blood causing its blood levels to rise.

It primarily occurs because enough insulin is not produced by the pancreas of the pregnant woman with GDM, which leads to high blood sugar levels.

Almost all pregnant women have higher blood sugar levels but within the normal range and cannot be considered diabetic. During pregnancy, certain hormones are produced by the placenta to facilitate the moving of nutrients from the mother to the baby through the placenta.

Some other placental hormones act to prevent the mother’s blood sugar from falling. They do this by blocking the action of insulin. During the course of pregnancy, this puts the mother at greater risk of attaining higher blood sugar levels and gestational diabetes, especially during the 3rd trimester.

In normal cases, the mother’s body produces more insulin to combat these high blood sugar levels and promote the uptake of blood sugar by the cells to produce energy. The mother’s pancreas is able to produce this additional insulin and this quantum can be thrice as much insulin as it normally does.

Now, when the mother’s pancreas is not able to produce the required additional amount of insulin (as in GDM) to keep blood sugar within normal limits, blood sugar levels rise above the normal limits and she develops gestational diabetes.

Factors that increase your risk of gestational diabetes

The following factors increase your risk of gestational diabetes.

  • Family history of diabetes
  • Increased maternal age: If you are more than 35 years of age
  • If you have high blood pressure
  • If you are 20% or more overweight than what your weight should normally be. Obesity in pregnancy is a common risk factor
  • Previous history of stillbirth or miscarriage or having a baby with a birth defect
  • Previous history of giving birth to a larger baby weighing 9 pounds or more
  • Detection of sugar in your urine
  • History of high blood sugar levels or gestational diabetes in a previous pregnancy
  • If you have excess amniotic fluid during your current pregnancy
  • Ethnicity: – If you are Black, Hispanic, Native American, Pacific Islander, or Asian, you are at greater risk of developing gestational diabetes.
  • If you are a smoker, your risk doubles.

These factors increase your risk and you should be wary during your pregnancy and observe diabetic discipline and regular screening.

Even with these risk factors, you may not contract gestational diabetes. And also note that many women who develop gestational diabetes (about half of them) do not harbor any of these risk conditions.