What is Gestational Diabetes?

Gestational Diabetes Mellitus (GD) is the finding of high blood sugar levels during pregnancy. Pregnancy places a higher level of insulin demand on the body. This occurs because hormones that are released from the placenta causes the expectant mother’s body to become more insulin resistant.

Gestational Diabetes Concept

Image Credit: Chompoo Suriyo/Shutterstock.com

Normally, most pregnant women can offset the effects of these hormones by producing more insulin. However, some are unable to ramp up their insulin production during pregnancy, and as a consequence, their blood glucose levels are raised beyond what’s considered normal. For most healthy people, this falls within the range of 4.0 to 5.4 mmol/L when fasted, or up to 7.8 mmol/L in the two hours following a meal.

Blood sugar

Our main source of energy is glucose, which we obtain from our diets, particularly in foods rich in carbohydrates, such as rice, pasta, bread, potatoes, and cereals.

Our body has also evolved to be able to produce its short-term supply of glucose in the liver from the storage of other molecules when necessary. Without a constant supply of glucose, we would soon become energy deficient and die.

Insulin and diabetes

The islet cells of the pancreas are responsible for the production of insulin. Insulin is a hormone that lowers glucose in the blood by allowing it to enter our cells. This is necessary for us to make proper utilization of glucose to survive. Without insulin, glucose is useless and can cause a wide range of destructive consequences when it is allowed to remain elevated in our bloodstream.

In GD, the expectant mother produces too little insulin to stimulate adequate uptake of glucose from the bloodstream by cells. The level of glucose in the blood, therefore, remains high. This is in contrast to two other main types of diabetes mellitus – type 1 diabetes mellitus (T1DM) and type 2 diabetes mellitus (T2DM).

In T1DM the body produces very little to no insulin, and symptoms usually manifest early on in life, whereas in T2DM the body fails to produce enough insulin to meet its requirements and/or the cells do not respond adequately to the amount of insulin produced by the pancreas.

Risk factors for developing GD and risks for the unborn child

Expectant mothers at risk of developing GD are those who had GD in a previous pregnancy, as well as those who have previously given birth to children who were 4.5kg or more.

Furthermore, pregnant women who have higher body mass indices (i.e. more than 30), and those who have a genetic predisposition to diabetes are also at risk.  There also appears to be a higher prevalence of GD among women who come from ethnic minority backgrounds.

Macrosomia, which is a condition in which a developing baby grows too much in utero is one of the most common consequences of GD. As can be imagined, this occurs because of the surplus of glucose being transferred to the growing baby via the placenta. This is particularly problematic as the larger the baby, the less safe it becomes for vaginal delivery.

Likewise, GD increases the risk of pre-eclampsia, which is dangerously elevated blood pressure during pregnancy. The growing baby is also at risk of stillbirth and preterm delivery.

These risks can be averted to a large degree with proper obstetric support throughout pregnancy. This includes regular check-ups, blood glucose monitoring, and maintaining healthy lifestyle choices with regards to weight, diet, and levels of activity.

Diagnosis and management of GD

GD may be diagnosed with the help of an oral glucose tolerance test (OGTT). OGTT confirms GD if fasting blood sugar levels are over 5.6 mmol/L, or if there is a glucose level of 7.8 mmol/L or more in the two hours following a meal.

Gestational diabetes can be monitored by routine and regular blood sugar testing, especially in women who have previously had GD. Blood glucose should be checked before and after the main meals of the day, and the aim should be to keep this level within the normal ranges.

Dietary management is crucial. Women who find themselves outside the referenced normal ranges should reduce their portions of carbohydrate intake and distribute their meals as evenly as possible throughout the day.

Additionally, they should consider different types of carbohydrate sources. Foods with lower glycemic indices are better for considerations, as these foods have a slower rate of being absorbed and thus have a positive effect on the rate of control of blood sugar levels.

In addition to diet, women are also advised to ensure regular exercise, which assists the body in controlling blood sugar. Under normal circumstances, moderate activity in healthy women should not do any harm to the growing baby.

Recreational exercise where strength is conditioned may also be beneficial. Despite dietary control and lifestyle modification, some women may require medications, such as insulin or metformin to bring their blood sugar level under control.

Updated on 21st July 2020 by Dr. Damien Jonas Wilson

Further Reading

Last Updated: Feb 23, 2023

Dr. Ananya Mandal

Written by

Dr. Ananya Mandal

Dr. Ananya Mandal is a doctor by profession, lecturer by vocation and a medical writer by passion. She specialized in Clinical Pharmacology after her bachelor's (MBBS). For her, health communication is not just writing complicated reviews for professionals but making medical knowledge understandable and available to the general public as well.


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