What is gestational diabetes? Let’s look at symptoms, causes, and treatments

Nov 13, 2023 | Pregnancy

Gestational diabetes (GDM) is a condition in which a woman without pre-existing diabetes develops high blood glucose levels during pregnancy. 

GDM can lead to complications for both the mother and the baby. The baby might grow larger than usual, which can potentially lead to issues during the pregnancy or during delivery. After birth, babies of mothers with gestational diabetes might experience low blood glucose, jaundice, or breathing problems. Additionally, having had gestational diabetes increases a woman’s lifetime risk of developing Type 2 diabetes.

Most women with gestational diabetes can manage their condition through diet and exercise, but some may require medication such as metformin or insulin. 

At QUFW, we perform third trimester growth assessments for GDM generally from 28 weeks onwards.

This fact sheet answers these questions:

What is gestational diabetes?

Gestational diabetes (GDM) is a condition that may arise during pregnancy when the body can’t produce enough insulin to meet its needs. This leads to elevated blood glucose levels which can impact both mother and baby. Possible implications of GDM include:

  • The baby’s growth can be affected, which can sometimes increase risk during pregnancy
  • If a baby is larger due to diabetes in pregnancy, this can increase the risk of some complications during delivery, and may require an alteration to delivery plan – timing, or the way that you deliver your baby
  • Post-birth, the baby may experience low blood glucose, jaundice, or breathing problems
  • Increased lifetime risk of type 2 Diabetes for women who have had gestational diabetes diagnosed in a pregnancy

It’s called “gestational” diabetes because it originates during gestation, or the pregnancy period.

How is gestational diabetes different from type 1 and type 2 diabetes?

Each of these forms of diabetes is characterised by high blood glucose levels, but they arise from different causes and manifest in different ways. Here’s a breakdown of the distinctions:

Gestational Diabetes (GDM)

  • Onset: Only develops during pregnancy.
  • Cause: Pregnancy results in the production of hormones that can make cells less sensitive to insulin. In some women, the body can’t produce enough insulin to transport the glucose into the cells, leading to elevated blood glucose levels.
  • Management: Often managed with dietary changes, exercise, and monitoring. Some women might need medication (either tablets, injections, or both).
  • Post-pregnancy: Usually resolves after giving birth, but women who had GDM are at a higher risk for developing type 2 diabetes later in life.
  • Risk: Babies born to mothers with uncontrolled gestational diabetes are at a higher risk for problems like obesity and type 2 diabetes.

Type 1 Diabetes (T1DM)

  • Onset: Typically manifests in childhood or adolescence, but can appear in adults.
  • Cause: An autoimmune reaction where the body’s defence system attacks the insulin-producing cells in the pancreas, leading to little or no insulin production.
  • Management: People with T1DM require lifelong insulin therapy – this can be administered through injections or an insulin pump.
  • Chronic Condition: This is a lifelong condition and does not go away.
  • Risk: Without proper management, T1DM can lead to various complications in many parts of the body.

Type 2 Diabetes (T2DM)

  • Onset: More common in adults but can also appear in younger individuals, especially with rising childhood obesity rates.
  • Cause: The body either resists the effects of insulin, meaning it doesn’t use insulin efficiently, or it can’t produce enough insulin to maintain normal blood glucose levels.
  • Management: Can often be managed with lifestyle changes like diet and exercise, but some people also need medication.
  • Chronic Condition: Like T1DM, this is a lifelong condition. However, with effective management, some individuals can revert their blood glucose levels back to normal.
  • Risk: Uncontrolled T2DM can lead to various health complications, similar to those of T1DM.

Diabetes – MODY

This is the name given to the Maturity Onset of Diabetes in the Young (MODY). It is a rare type of Diabetes where there has been a genetic change in either the individual or by inheriting the genetic change from a parent. 

  • Onset: it generally affects children, adolescents and young adults and often manifests before the age of 25.
  • Cause: The body either resists the effects of insulin, meaning it doesn’t use insulin efficiently, or it can’t produce enough insulin to maintain normal blood glucose levels.
  • Management: Can often be managed with lifestyle changes like diet and exercise, but some people also need medication.
  • Chronic Condition: Like T1DM, this is a lifelong condition. However, with effective management, some individuals can revert their blood glucose levels back to normal.
  • Risk: Uncontrolled T2DM can lead to various health complications, similar to those of T1DM.

What causes gestational diabetes?

Multiple factors contribute to the onset of GDM during pregnancy. Here are some of the primary causes and contributing factors:

  • Pregnancy Hormones: During pregnancy, the placenta supports the growing fetus by producing several necessary hormones. Some of these hormones can interfere with the mother’s insulin (which helps regulate blood glucose levels), making her body less sensitive to insulin. This is a condition called insulin resistance.
  • Increased Demand for Insulin: As the pregnancy progresses, especially during the second and third trimesters, the mother’s body requires two to three times more insulin than usual. If her pancreas can’t produce enough insulin to meet this demand, blood glucose levels rise, resulting in gestational diabetes.
  • Excess Weight: Being overweight or obese prior to pregnancy, or gaining excessive weight during pregnancy, can increase a woman’s risk of developing gestational diabetes. Excess weight can cause increased insulin resistance.
  • Genetic Factors: Women with a family history of diabetes may have a higher risk of developing GDM. Specific genes have also been linked to the susceptibility of developing gestational diabetes.
  • Age: Women older than 25 years are at a greater risk of developing gestational diabetes compared to their younger counterparts.
  • Ethnicity: Women from certain ethnic backgrounds, including African, Hispanic, Native American, South or East Asian, and Pacific Islander, are at a heightened risk.
  • Multiple pregnancy: carrying twins, triplets or higher order multiples increases the chance of developing GDM
  • Previous GDM: Having gestational diabetes in a previous pregnancy significantly increases the risk of experiencing it in subsequent pregnancies.
  • Previous delivery of a large baby: If a woman has previously delivered a baby weighing more than 9 pounds (4.1 kilograms), she might be more likely to develop gestational diabetes.
  • Polycystic Ovary Syndrome (PCOS): Women with PCOS, a common condition characterised by irregular menstrual periods, excess hair growth, and obesity, are at increased risk of GDM.
  • Other health conditions: Conditions like hypertension or having a slightly elevated blood glucose level before pregnancy (known as prediabetes) can also increase the risk.

It’s worth noting that while these factors can increase the risk, gestational diabetes can develop in women without any of these risk factors. Early screening and management are crucial to ensure the health of both the mother and the baby.

What symptoms might suggest a woman has developed gestational diabetes?

Gestational diabetes often doesn’t present with noticeable symptoms, which is why routine screening during pregnancy is so important. However, when symptoms do occur, they may include:

  • Increased Thirst: A noticeable increase in thirst compared to what’s typical for the individual’s pregnancy.
  • Increased Urination: Needing to urinate more often than usual or in larger quantities.
  • Fatigue: While fatigue is common in pregnancy, sudden or excessive tiredness might signal a change in blood glucose levels.
  • Glucose in the Urine: This is usually detected during a routine prenatal visit rather than being a symptom the pregnant person notices.
  • Blurred Vision: High blood glucose levels can cause fluid levels in the body to shift, impacting the lenses of the eyes and leading to blurry vision.
  • Increased Hunger: An increased appetite, particularly after eating.
  • Nausea and Vomiting: Although this can be a symptom of a typical pregnancy, particularly in the first trimester, sudden onset later in pregnancy might be indicative.
  • Recurrent Infections: Such as bladder infections or yeast infections.
  • Unexplained Weight Loss: Despite having a good appetite, some women may experience unexplained weight loss.

It’s essential to understand that many of these symptoms can also be typical experiences during pregnancy or be related to other conditions. Therefore, any woman experiencing these symptoms during pregnancy should promptly consult her healthcare provider. Again, because many women with gestational diabetes may not exhibit symptoms, routine screening during the second trimester is standard practice in many countries.

At what point during pregnancy is gestational diabetes most commonly diagnosed?

GDM is most commonly diagnosed during the second trimester of pregnancy. In most pregnancies, screening will be recommended with a GTT between 26 and 28 weeks of pregnancy. However, if a woman has risk factors for the development of GDM, she will often also be recommended to undertake additional screening in early pregnancy. . 

How is gestational diabetes diagnosed? What tests are involved?

GDM is diagnosed through specific tests that assess how a pregnant woman’s body manages glucose. Here’s a streamlined explanation of the process:

HbA1c: 

  • This is a single non-fasting blood test which tests for glycosylated haemoglobin
  • This gives an indication of blood glucose levels over the prior 3 months
  • It is only helpful in pregnancies when performed <14 weeks gestation, but if done at this stage, can avoid the need for a full early GTT in women with risk factors
  • HbA1C is utilised to monitor glycaemic control during pregnancy in women with pre-existing diabetes – and to inform fetal risk 

Oral Glucose Tolerance Test (OGTT):

  • The woman fasts overnight, and her blood glucose level is initially measured.
  • She then consumes a glucose-rich solution.
  • Blood glucose levels are tested several times over the next 2 to 3 hours.
  • If two or more of these readings exceed a certain threshold, a diagnosis of gestational diabetes is confirmed.

Are there specific ultrasound findings that may indicate or be associated with gestational diabetes?

There are specific ultrasound findings that may suggest the presence of GDM or indicate that a fetus has been affected by the mother’s elevated blood glucose levels. It’s important to note that while these findings can be associated with GDM, they are not diagnostic on their own and can be seen in pregnancies without GDM. Here are some of the ultrasound findings:

  • Macrosomia: This is when the fetus is significantly larger than average for its gestational age. GDM increases the risk of a fetus developing large body size due to the increased glucose supply.

Estimated fetal weight

  • Increased Abdominal Circumference: The fetus might have a disproportionately large abdominal circumference compared to its head circumference.

Increased abdominal circumference

  • Increased Amniotic Fluid (Polyhydramnios): Mothers with GDM may produce more amniotic fluid. This happens because the fetus might produce more urine in response to the mother’s higher blood glucose levels.

Amniotic Fluid Index

  • Cardiac Abnormalities: Some studies suggest that babies of mothers with GDM might have slight alterations in cardiac function or structure.
  • Mature Placenta: An earlier maturation of the placenta can sometimes be seen on ultrasound in women with GDM.
  • Subcutaneous Fat Thickness: Some studies have used the measurement of subcutaneous fat thickness in the fetus as an indicator of its overall size and potential exposure to high glucose levels.

Remember, while these findings can be associated with GDM, they don’t confirm the diagnosis. If such findings are detected on ultrasound, further investigations, including glucose testing, are essential to determine the presence of gestational diabetes.

What lifestyle changes can help manage or reduce the risk of gestational diabetes?

Managing or reducing the risk of gestational diabetes (GDM) often involves lifestyle changes, particularly in the areas of diet and exercise. Some of these changes include:

Dietary Modifications:

  • Balanced Meals: Eating balanced meals with a mix of carbohydrates, protein, and healthy fats can help stabilise blood glucose levels.
  • Complex Carbohydrates: Opt for whole grains, legumes, and vegetables. These take longer to digest, leading to a more gradual rise in blood glucose.
  • Limit Sugary Foods and Drinks: Reduce the intake of sweets, sugary soft drinks, and other foods and drinks with added sugars.
  • Fibre: High-fibre foods, like whole grains, fruits, and vegetables, can help manage blood glucose.
  • Limit Saturated and Trans Fats: Opt for healthier fats like those found in olive oil, nuts, and avocados.

Exercise:

  • Regular Activity: Aim for at least 30 minutes of moderate activity most days of the week. This can include walking, swimming, or prenatal yoga.
  • Strength Training: Light resistance training can help improve insulin sensitivity. Always consult a healthcare provider before starting any new exercise regimen during pregnancy.
  • Consistency: Regular, consistent physical activity helps the body use insulin more efficiently.
  • Monitor Blood Glucose: For those already diagnosed with GDM, it’s important to monitor blood glucose levels after exercise, as physical activity can lower blood glucose.

Additional Lifestyle Measures:

  • Maintain a Healthy Weight: Gaining the recommended amount of weight during pregnancy, based on a healthcare provider’s advice, can help manage or reduce the risk of GDM.
  • Avoid Smoking: Smoking can increase the risk of various pregnancy complications, including GDM.
  • Manage Stress: Chronic stress can affect insulin sensitivity. Techniques like meditation, deep breathing exercises, and prenatal yoga can help manage stress during pregnancy.
  • Regular Monitoring: For those at risk or diagnosed with GDM, regular monitoring of blood glucose levels is crucial.

It’s essential for pregnant women, especially those at risk for GDM, to work closely with their healthcare providers. This ensures they are making the best lifestyle choices for themselves and their babies. A registered dietitian or a diabetes educator can also offer personalised strategies and support.

Are medications such as insulin ever required to treat gestational diabetes?

While many women with GDM can manage their blood glucose levels with lifestyle changes alone, some do require medications to maintain their blood glucose within the target range. 

It is important to remember that fetal risk – both during pregnancy and after birth – relates to the quality of the diabetic control, and not to the diagnosis of GDM.

What are the potential complications if gestational diabetes is not managed effectively?

If GDM is not managed effectively, it can lead to various complications for both the mother and the baby. Here are some of the potential complications:

For the Baby:

  • Macrosomia: Babies of mothers with uncontrolled GDM might grow too large due to excess glucose crossing the placenta. This can make vaginal delivery difficult and increase the risk of birth injuries.
  • Early (preterm) Birth: High blood glucose might increase the risk of early labour or require early delivery for the health of the baby.
  • Respiratory Distress Syndrome: Babies born early might face respiratory issues because their lungs aren’t fully matured.
  • Low Blood Glucose (Hypoglycemia): Shortly after birth, babies might have low blood glucose levels, which can lead to seizures if not treated promptly.
  • Jaundice: Babies of mothers with GDM have a higher risk of developing jaundice due to the breakdown of red blood cells, leading to a buildup of bilirubin.
  • Type 2 Diabetes Risk: It is unlikely that your baby will be born with diabetes. However, babies exposed to high blood glucose in the womb are at a higher risk of obesity and type 2 diabetes in their later life.
  • Stillbirth: In severe cases, uncontrolled GDM can increase the risk of stillbirth.

For the Mother:

  • High Blood Pressure and Preeclampsia: GDM increases the risk of high blood pressure and its severe form, preeclampsia, which can be life-threatening for both the mother and the baby.
  • Delivery Complications: Due to the baby’s larger size, there’s an increased risk of needing a C-section or encountering complications during vaginal delivery.
  • Future Diabetes: Women with GDM have a higher risk of developing type 2 diabetes later in life.
  • GDM in Subsequent Pregnancies: Having GDM in one pregnancy increases the risk of its recurrence in subsequent pregnancies.

What is the likelihood of a woman developing type 2 diabetes after experiencing gestational diabetes?

Women who have had GDM are at an increased risk of developing type 2 diabetes later in life. The exact risk can vary based on multiple factors, including but not limited to body weight, age, and lifestyle.

Further reading

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