Gestational Diabetes

What is gestational diabetes? 

Gestational diabetes mellitus (GDM) is a type of diabetes that develops during pregnancy in women who did not previously have diabetes (though they may have had GDM before). It typically arises in the second or third trimester and is characterised by high blood glucose (sugar) levels resulting from hormonal changes that impair insulin function. During pregnancy, the placenta produces hormones that support the baby’s growth, but these hormones can also interfere with the mother’s insulin action — a process known as insulin resistance. When the pancreas cannot produce enough insulin to overcome this resistance, blood glucose levels rise, which results in gestational diabetes.

This condition occurs in one in five Singaporean women who are pregnant. This is higher than international rates and is attributed to later age of pregnancy and an increased asian predisposition to GDM [1].

While it often resolves after childbirth, gestational diabetes increases the risk of developing type 2 diabetes (see other article/hyperlink) later in life for both mother and child. It can also pose risks during pregnancy and delivery, including excessive birth weight (macrosomia), low blood sugar in the baby at birth, preterm birth, and the need for caesarean section.

Fortunately, with early diagnosis, appropriate management, and close monitoring, most women with gestational diabetes can have healthy pregnancies and deliver healthy babies. 

Management usually involves dietary changes, regular physical activity, blood sugar monitoring, and in some cases, insulin or oral medication.

What causes gestational diabetes?

Gestational diabetes develops when hormonal changes during pregnancy impair the body’s ability to use insulin effectively. As the placenta grows, it produces hormones that help sustain the pregnancy but also reduce the action of insulin, leading to a condition known as insulin resistance. To maintain normal blood glucose levels, the pancreas needs to produce significantly more insulin. When it is unable to do so, glucose builds up in the bloodstream, resulting in gestational diabetes.

Several biological and physiological processes contribute to this condition:

• Placental hormone production — hormones such as human placental lactogen, oestrogen, progesterone, and cortisol rise during pregnancy. These hormones interfere with insulin signalling, especially in the second and third trimesters where the levels of these hormones start to peak.

• Increased insulin resistance — as pregnancy progresses, insulin resistance naturally increases to ensure more glucose is available for the growing baby. In some women, this resistance becomes excessive, preventing effective glucose uptake by cells.

• Inadequate insulin response — the pancreas may be unable to meet the rising demand for insulin. This insufficient insulin production leads to elevated blood sugar levels as some women may have a mild, previously undetected dysfunction in their pancreatic beta cells (which produce insulin). This makes it harder to adapt to the demands of pregnancy.

These changes are a normal part of pregnancy, but when the balance between insulin resistance and insulin production is disrupted, gestational diabetes can occur.

What are the complications of gestational diabetes? 

Gestational diabetes, when not well managed, can lead to several complications that may affect both the mother and the baby during pregnancy, delivery, and beyond. It is important to understand the potential risks so that timely monitoring and intervention can be put in place.

Complications affecting the baby

• Macrosomia (large birth weight) — high maternal blood glucose levels can cross the placenta, causing the baby’s pancreas to produce more insulin. This may lead to excessive fat accumulation and growth, increasing the risk of birth weight over 4.5 kg, which can make vaginal delivery more difficult and raise the likelihood of birth injuries.

• Preterm birth — poorly controlled gestational diabetes can increase the risk of early labour, either spontaneously or through medical induction, particularly if complications arise.

• Neonatal hypoglycaemia — right after birth, babies exposed to high maternal glucose may produce excess insulin, which can lead to low blood sugar levels soon after delivery.

• Respiratory distress syndrome — babies born to mothers with gestational diabetes may have underdeveloped lungs due to high blood sugar levels and insulin, especially if born early, which can make breathing difficult.

• Increased risk of obesity and type 2 diabetes later in life — children born to mothers with gestational diabetes have a higher lifetime risk of developing metabolic conditions, including obesity and type 2 diabetes.

Complications affecting the mother

• Increased risk of pre-eclampsia — gestational diabetes raises the likelihood of developing high blood pressure and pre-eclampsia, a potentially serious condition that can threaten both maternal and foetal health.

• Delivery complications — the risk of requiring a caesarean section is higher, particularly with large babies or if labour does not progress normally.

• Higher chance of developing type 2 diabetes — women who have had gestational diabetes have a significantly increased risk of developing type 2 diabetes later in life. Without lifestyle changes or medical follow-up, this risk can become apparent within five to ten years after delivery.

• Recurrence in future pregnancies — once a woman has had gestational diabetes, the chances of it recurring in future pregnancies is considerably higher.

At The Metabolic Clinic, we closely monitor mothers throughout pregnancy and provide comprehensive postnatal care to reduce the risk of long-term complications. Early detection, personalised treatment plans, and continuous support are key to minimising the impact of gestational diabetes.

What are the signs and symptoms of gestational diabetes? 

Gestational diabetes often develops without any noticeable symptoms, which is why routine screening between 24 and 28 weeks of pregnancy is essential. Though rare, some women may experience mild, non-specific symptoms related to high blood sugar levels. These may include:

• Increased thirst — feeling unusually thirsty, even after drinking fluids.

• Frequent urination — needing to urinate more often than usual, particularly at night.

• Fatigue — feeling more tired than expected during pregnancy, beyond normal levels.

• Dry mouth — persistent dryness in the mouth, often accompanied by thirst.

• Blurred vision — occasional episodes of unclear or fuzzy vision.

• Recurrent infections — especially urinary tract infections or vaginal thrush.

• Unexplained weight changes — either rapid weight gain or difficulty managing weight during pregnancy.

Because these symptoms can overlap with common pregnancy experiences, screening is the most reliable way to detect gestational diabetes early and begin appropriate care.

Who is at risk of gestational diabetes in Singapore? 

Gestational diabetes mellitus (GDM) is a prevalent condition in Singapore, affecting approximately 15–20% of pregnancies. While it can develop in any pregnant woman, certain factors elevate the risk. Understanding these risk factors is crucial for early detection and effective management.​

Key risk factors for GDM in Singapore include:

• Age over 40 years — advancing maternal age is associated with reduced insulin sensitivity, increasing the risk of GDM.

• Body Mass Index (BMI) ≥ 23 kg/m² — among Asian populations, a BMI of 23 or higher is considered overweight and is linked to a higher risk of insulin resistance.

• Family history of diabetes — having a parent or sibling with diabetes significantly raises the chance of developing gestational diabetes.

• Previous diagnosis of GDM — women who have had gestational diabetes in a past pregnancy are more likely to experience it again.

• History of delivering a large baby (≥ 4.5 kg) — prior delivery of a macrosomic baby suggests possible undiagnosed glucose intolerance in earlier pregnancies.

• Polycystic ovary syndrome (PCOS) — this hormonal condition is often associated with insulin resistance, increasing the likelihood of GDM.

• Belonging to higher-risk ethnic groups — women of South Asian, Southeast Asian, Middle Eastern, or African-Caribbean descent have a greater predisposition to GDM.

• Past poor pregnancy outcomes — a history of unexplained stillbirth or other complications can be linked to undetected gestational diabetes.

It's important to note that GDM can occur even in the absence of these risk factors. Therefore, routine screening between 24 and 28 weeks of gestation is recommended for all pregnant women. 

How can I prevent gestational diabetes? 

Gestational diabetes can’t always be avoided, as some factors like age and family history are beyond control. However, there are several steps you can take before and during pregnancy to reduce your chances of developing it. These lifestyle choices help support your body’s ability to use insulin more effectively and keep blood sugar levels in a healthy range.

Steps that may lower your risk of gestational diabetes include: 

• Achieving a healthy weight before pregnancy — if you are planning to conceive, try to reach a healthy weight first. Even a small amount of weight loss can help improve how your body handles insulin.

• Staying active — regular physical activity, like brisk walking, swimming, or prenatal yoga, improves insulin sensitivity and helps regulate blood sugar levels. Aim for at least 30 minutes of moderate activity most days of the week.

• Eating a balanced diet — focus on whole foods, including vegetables, whole grains, lean proteins, and healthy fats. Limit added sugars and highly processed carbohydrates that cause sharp spikes in blood sugar.

• Avoiding excessive weight gain during pregnancy — gaining too much weight too quickly during pregnancy increases the strain on your body’s insulin response. Follow your doctor’s recommendations on healthy weight gain based on your pre-pregnancy BMI (those who were overweight prior to pregnancy should gain less weight than those who were of normal or underweight).

• Monitoring risk factors early — if you have a higher risk due to age, BMI, or family history, talk to your doctor early in your pregnancy. Early screening and advice can help you take action before glucose levels rise.

How is gestational diabetes diagnosed?

Gestational diabetes is usually diagnosed between the 24th and 28th week of pregnancy, when insulin resistance tends to increase. However, women with higher risk factors, such as a history of gestational diabetes, obesity, or a family history of diabetes, will be screened earlier.

Oral Glucose Tolerance Test (OGTT): 

This is the standard method used to diagnose gestational diabetes.

• You will be asked to fast overnight.
• A fasting blood sample is taken first.
• You will then drink a sweet glucose solution.

Blood samples are taken at specific intervals, one and two hours after drinking, to measure how your body processes the glucose.

A pregnant woman is diagnosed with GDM if any one of the following three plasma glucose values is met or exceeded:

• Fasting: ≥ 5.1 mmol/L (or ≥ 92 mg/dL)
• 1-hour post-OGTT: ≥ 10.0 mmol/L (or ≥ 180 mg/dL)
• 2-hour post-OGTT: ≥ 8.5 mmol/L (or ≥ 153 mg/dL)

These tests are safe for both mother and baby. Early detection allows for timely management through lifestyle adjustments, blood sugar monitoring, and, if needed, medication. 

How to manage gestational diabetes? 

Managing gestational diabetes involves keeping blood sugar levels within a safe range to protect both mother and baby. This is usually achieved through a combination of lifestyle changes, monitoring, and medical care. Most women with gestational diabetes can manage the condition effectively and go on to have healthy pregnancies and deliveries.

Lifestyle changes

Diet and exercise are the first line of management for gestational diabetes.

• Choose whole grains, vegetables, lean protein, and healthy fats while limiting processed foods, sugary snacks, and refined carbohydrates.

• Eating small, frequent meals and combining carbohydrates with protein or fibre can help avoid sharp spikes in blood sugar.

• Moderate physical activity, such as walking, prenatal yoga, or swimming, improves how your body uses insulin. Most women can safely exercise during pregnancy, but it’s important to check with your doctor first. Dr. Dinesh often advises his patients to take a walk after the largest meal of the day to reduce sugar rise after that meal.

Blood sugar monitoring

Once the diagnosis is confirmed, you will likely be asked to monitor your blood glucose levels several times a day, usually before meals and two hours after eating. This helps you and your care team understand how your body is responding to food, activity, and any treatments. 

Keeping a log of your readings helps in making timely adjustments to your care plan. Your doctor or diabetes educator will guide you on how to use a glucometer, what targets to aim for, and how to respond to high or low readings.

At The Metabolic Clinic, many of our patients prefer to use continuous glucose monitoring systems that are able to monitor sugar levels continuously for many days at a time without the prick of a finger. 

Medication 

If lifestyle changes alone don’t keep your blood sugar within the target range, your doctor may prescribe medication.

• Insulin is the most commonly used treatment and is safe during pregnancy.

• In milder cases, metformin may be considered prior. 

Your doctor will determine the right type and dose based on your blood sugar patterns and pregnancy progress.

Monitoring the baby 

Gestational diabetes can affect the baby’s growth and development, so regular monitoring is essential.

• You may have additional ultrasounds to track foetal growth, fluid levels, and overall well-being.

• Your obstetrician may also recommend foetal movement tracking or non-stress tests in the third trimester.

• In some cases, delivery may be scheduled earlier if there are concerns about the baby’s size or placenta function.

Follow-up after delivery

In most cases, gestational diabetes resolves after childbirth. However, ongoing follow-up is important. You will need a repeat glucose test 6 weeks after delivery to check if your blood sugar has returned to normal as some ladies may have persistent diabetes

Women who have had gestational diabetes are at higher risk of developing type 2 diabetes in the future, so regular blood sugar screening is recommended every 1 to 3 years. However, maintaining a healthy diet, staying active, and keeping a healthy weight post-pregnancy can significantly reduce this risk.

Summary 

Gestational diabetes is a temporary form of diabetes that can develop during pregnancy, often without clear symptoms. It occurs when pregnancy-related hormones interfere with insulin function, leading to elevated blood sugar levels. If not managed properly, it can cause complications for both mother and baby, including preterm birth, large birth weight, and long-term health risks. However, it’s also important to remember that with the right support, most women can manage gestational diabetes effectively and have a healthy pregnancy with no complications. 

If you are concerned about your risk or have been diagnosed with gestational diabetes, schedule a consultation with us for personalised guidance and comprehensive care throughout your pregnancy.

Frequently Asked Questions (FAQs) 

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References:

1. (Ref: Lazarus MA, Lee VV, Ong DLS, Yew TW, Shorey S, Young D, Eriksson JG. Understanding the Experiences of Women with Gestational Diabetes in Singapore: A Qualitative Study. Int J Womens Health. 2025 Jun 8;17:1711-1724. doi: 10.2147/IJWH.S517739. PMID: 40510814; PMCID: PMC12161141.)