Gestational Diabetes – Causes, Risks and Results

There are various types of diabetes including type 2 (T2D) and type 1 (T2D) diabetes. Yet, there is another type of diabetes that commonly occurs in women, named gestational diabetes. It appears during pregnancy and can endure for a short while after the baby is born.

What is Gestational Diabetes (GD)?

Gestational diabetes is the term used to describe diabetes that is present during but not before or after the pregnancy. It derives its name from the Latin word gestare “to carry” – specifically referring to within the womb. GD may best be defined as glucose intolerance that occurs only during pregnancy.[1] It is not to be confused with diabetes prior to pregnancy. Pre-pregnancy diabetes is called pre-gestational diabetes.

Who is at Risk?

The statistics show that between 2% and 5% of all pregnant women will get GD.2  Rates overall vary from 1.4 to 14%. Rates are higher among the following groups:

  • Native American women
  • African American
  • Hispanic women
  • Asian women
  • Mothers-to-be who are older than 35
  • Obese women

There are other risk factors associated with those who may become diabetic during pregnancy. This includes a medical history of hypertension or polycystic ovarian syndrome. There is also emerging evidence that GD may have a genetic element.3

What causes GDM?

Hyperglycemia (raised blood glucose) during pregnancy is said to result because the placenta (afterbirth) secretes hormones that cause a resistance to the effect of insulin on the cell walls. As a result, it prevents the absorption of glucose in the blood that is ready to be transported into the cell by the insulin effect.  Instead, the glucose has to stay in circulation. This activates the pancreas to increase the manufacturing of insulin by as much as 3 times the normal level in an attempt to keep the glucose at the right level.

Meanwhile, the placenta, acting as a barrier between the mother and the fetus, allows glucose but not insulin to pass from the mother’s blood to the fetus.4

What are the Symptoms and How Is It Detected?

It is not easy to diagnose initially. Symptoms include polyuria (frequency of urination) and an increase in urinary tract infections.4  Sometimes the polyuria is not recognized as a symptom of diabetes because increased frequency of urination is common in non-diabetic pregnant women.

It is possible to detect GD through routine medical testing. It should start as a part of routine prenatal care. Most women will be routinely tested for diabetes around 26 weeks gestation, but they may be tested much earlier if they have some of the risk factors lists above. If a woman is tested early and is found to not have GD, she will be tested again at approximately 26 weeks. Whenever possible, medical doctors will follow this procedure when testing:

  • At 26 weeks, give the so-called “50 gram challenge” – a test in which the patient is given that much glucose to drink (or eat) and then a blood sample is taken 60 minutes later. Some doctors use jelly beans instead of cola
  • If the sample does not produce clear results, the patient will be asked to give a blood sample. This is followed by a drink of 75 g of glucose – on an empty stomach (fasting)  – and another blood test

The results of these tests will indicate whether you have “normal” blood sugar levels, have impaired glucose tolerance or have gestational diabetes. If you are a member of a high risk group, it’s important to have this glucose test at an early stage of pregnancy. It is important to identify the risk as soon as possible in order to prevent harm to the fetus.

Affect on the Fetus

The effects of GD are not restricted to the mother alone. Research indicates there are several effects upon the fetus and new born infant. These include:

  • Birth weight above the 90th percentile – a condition called macrosmia. The baby is overweight but is not healthy and requires special needs
  • Dystocia, or the baby becoming stuck on the way out during delivery, often requiring assistance to progress
  • Cesarean deliveries
  • Neonatal hypoglycemia

What is done for the persons diagnosed with GDM?

This is a serious problem. It requires the care of a specialist – perhaps a high risk obstetrician and a nutritionist or dietician. The focus should be on specific aspects of care, many of them similar to those recommended for diabetes. This includes an appropriate diet and prescribed exercise program. In certain cases, it has become the norm to prescribe and administer certain oral anti-diabetic agents. This is to help with the regulation of blood sugar levels and reduce the chances of the fetus receiving too much nutrition in the womb.

Long Term Issues

While it is common for GD to disappear after delivery, this is not the end of the problem. The risk of developing T2D within 10 years after giving birth can be as high as 70%. As a result, it is highly recommended that all GD patients be retested regularly. Glucose blood levels should be tested following delivery, before discharge, between 6 and 12 weeks after delivery, then at regular intervals. Tests should be administered at 1 year and then at every 3 years.


Research is slowly uncovering the causes of GD and the characteristics of those at highest risk. However, much more work is still required in order to discover and understand this disease. It is hoped that one day it will be possible to prevent gestational diabetes.


[1] Buchanan, TA; and  Xiang, AH (2005). “Gestational Diabetes Mellitus.” J Clinical Investigation, 115(3):485–491.

2 Gilmartin, A “B” H; Ural, SH; and Repke, JT (2008). “Gestational Diabetes Mellitus.” Rev Obstetrics Gynecology, 1(3): 129-134.

3 Buchanan, op.cit.

4 Gilmartin, op. cit.

This article was originally published July 12, 2012 and last revision and update of it was 9/10/2015.