Gestational Diabetes: What It Is, Who Is at Risk, and How to Test for It
Last updated: 25 Aug 2026
Gestational diabetes is one of the most common complications of pregnancy in Singapore. Between 1 in 4 and 1 in 5 pregnant women will develop it. That prevalence is among the highest in the world, higher than most Western countries and higher than many other countries in Southeast Asia.
Yet many women do not know they have it. And many who are diagnosed do not fully understand what it means for their health, their pregnancy, or their child's future risk of diabetes.
This guide explains gestational diabetes clearly: what it is, why it happens, who is at risk, and how testing works.
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What Is Gestational Diabetes?
Gestational diabetes is a condition in which a pregnant woman's blood sugar becomes elevated during pregnancy. Crucially, it develops only during pregnancy. If you did not have diabetes before you became pregnant, and you develop high blood sugar for the first time while you are pregnant, that is gestational diabetes.
It is temporary in the sense that blood sugar levels typically return to normal after delivery. In about 90 per cent of women with gestational diabetes, the condition resolves completely within weeks of giving birth. This is fundamentally different from Type 1 or Type 2 diabetes, which are lifelong conditions.
However, the term "temporary" can be misleading.
Gestational diabetes is not harmless just because it resolves after pregnancy. If left untreated or poorly managed during pregnancy, it can cause serious complications for both you and your baby. And the fact that you developed gestational diabetes is a significant marker of your future health risk. It signals that your body struggles to regulate blood sugar, a pattern that often persists after delivery.
Why Gestational Diabetes Happens
The mechanism behind gestational diabetes is well understood. During pregnancy, your placenta produces hormones that help sustain the pregnancy. These same hormones, particularly human placental lactogen, have a side effect: they block the action of insulin in your body. This is called insulin resistance.
Your pancreas normally compensates by producing more insulin to overcome this resistance and keep blood sugar normal. In most women, this works perfectly. The pancreas produces extra insulin, and blood sugar stays well controlled throughout pregnancy.
In some women, however, the pancreas cannot produce quite enough insulin to overcome the placental hormones. Blood sugar rises above the normal range, and gestational diabetes develops. This usually happens around the second trimester, which is why screening is recommended at 24 to 28 weeks of pregnancy.
It is important to understand that gestational diabetes is not caused by diet, weight, or lifestyle in the same way Type 2 diabetes sometimes is. You cannot "cause" gestational diabetes by eating poorly or not exercising. It is the result of hormonal changes inherent to pregnancy combined with your individual pancreatic capacity. That said, women who are overweight, sedentary, or already have some degree of insulin resistance are more likely to develop it.
Who Is at Higher Risk
Although gestational diabetes can occur in any pregnant woman, certain factors increase the likelihood significantly.
- Age - Women over 25 have higher risk than younger women. Risk continues to increase with age throughout the reproductive years.
- Family history of diabetes - If a parent or sibling has Type 2 diabetes, your risk of gestational diabetes is elevated. This reflects shared genetic predisposition to insulin resistance.
- Ethnicity - Singaporean women of Indian and Malay descent have higher rates of gestational diabetes compared to those of Chinese descent, though the condition affects all ethnic groups. This partly reflects genetic differences in insulin sensitivity and partly reflects socioeconomic factors affecting diet and activity levels.
- Overweight or obesity - A pre-pregnancy BMI above 25 kg/m² significantly increases risk. The higher your BMI, the higher your risk.
- History of gestational diabetes - If you developed gestational diabetes in a previous pregnancy, your risk of developing it again in future pregnancies is very high. Many women have gestational diabetes in more than one pregnancy.
- Polycystic ovary syndrome (PCOS) - Women with PCOS have insulin resistance as a core feature of the condition, making them much more likely to develop gestational diabetes when pregnant.
- Sedentary lifestyle - Women who exercise little and spend most of their day sitting are at higher risk than those who are regularly active.
- Previous pregnancy complications - If you gave birth to a very large baby, experienced recurrent miscarriages, or had stillbirth in a previous pregnancy, your risk of gestational diabetes is elevated for future pregnancies.
Having one risk factor means your risk is above average. Having multiple risk factors means you should definitely be screened, and possibly screened earlier than the standard 24 to 28 week window.
How Gestational Diabetes Is Screened and Diagnosed in Singapore
All pregnant women in Singapore are offered screening for gestational diabetes. The gold standard test is the oral glucose tolerance test, or OGTT.
Standard Screening: 24 to 28 Weeks
At your routine antenatal visit around 24 to 28 weeks of pregnancy, you will be offered the OGTT. Here is how it works.
- You will be asked to fast overnight (nothing to eat or drink except water for at least 8 hours). In the morning, you arrive at the clinic or hospital for the test. A baseline blood sample is drawn to measure your fasting blood glucose.
- You then drink a standardised glucose solution containing 75 grams of glucose. This is typically provided as a sweet beverage that you consume within five minutes.
- Blood samples are then taken exactly one hour after you drink the solution, and again at two hours after drinking it. Three blood glucose measurements are obtained: fasting, one-hour post-glucose, and two-hour post-glucose.
Diagnostic Thresholds
Gestational diabetes is diagnosed if any one of these three values exceeds the threshold:
- Fasting glucose: 5.1 mmol/L or higher
- One-hour glucose: 10.0 mmol/L or higher
- Two-hour glucose: 8.5 mmol/L or higher
If all three values are below these thresholds, your result is normal and you do not have gestational diabetes.
Early Screening for High-Risk Women
If you have significant risk factors (strong family history, previous gestational diabetes, PCOS, or being very overweight), your doctor may recommend screening earlier, at your first prenatal visit around the first trimester. If that early screening is normal, you will typically repeat the OGTT at the standard 24 to 28 week window, as gestational diabetes can develop later in pregnancy even if it was not present earlier.
What Happens if You Are Diagnosed
If your OGTT shows gestational diabetes, it is important to remember two things. First, it is manageable. Second, it requires active management.
Most gestational diabetes can be controlled with dietary changes and regular physical activity. Your doctor will refer you to a dietitian who specialises in pregnancy nutrition. You will receive guidance on carbohydrate choices, portion sizes, and meal timing. Regular gentle exercise, such as walking 30 minutes most days, helps improve insulin sensitivity.
Some women also benefit from blood glucose monitoring at home using a glucose meter. You may be asked to check your fasting glucose and blood sugar readings at certain times after meals to ensure levels remain in target range.
If lifestyle changes alone do not bring blood sugar to target, insulin therapy may be recommended. Insulin is safe in pregnancy and is the preferred medication for gestational diabetes. Some oral medications for diabetes are considered safe in pregnancy, but insulin remains first-line.
With appropriate treatment, the vast majority of gestational diabetes is managed successfully without complications.
After Delivery: What Comes Next
One to two weeks after delivery, your blood sugar will be checked again to confirm that gestational diabetes has resolved. In most cases, it will have.
However, developing gestational diabetes during pregnancy means you have a 35 to 60 per cent risk of developing Type 2 diabetes within the next 5 to 10 years. This is a significant lifetime risk, and it is crucial to monitor it.
Your doctor will recommend that you have a diabetes screening test at 6 to 12 weeks postpartum and then at least once every three years thereafter. Many doctors recommend annual screening for women with a history of gestational diabetes, particularly if you have other risk factors such as overweight or a family history of diabetes.
Lifestyle changes made during pregnancy can often be sustained after delivery. Women who maintain a healthy weight, exercise regularly, and eat a balanced diet significantly reduce their risk of progressing to Type 2 diabetes.
Information for Family
If you have been diagnosed with gestational diabetes, your partner and family members can play a supportive role. Gestational diabetes is not your fault. It is not a result of eating poorly or not trying hard enough. It is a physiological response to pregnancy that some women's bodies are predisposed to develop.
That said, managing gestational diabetes effectively does require active engagement with diet, activity, and medical monitoring. Support from your partner or family in making dietary changes, facilitating exercise, and attending medical appointments makes a real difference.
- For your partner: helping with household tasks so you have time to rest, joining you for walks or other physical activity, and helping with meal planning and preparation are practical ways to support.
- For family: being supportive of the dietary recommendations from your doctor and dietitian (avoiding pressure to eat foods that are not recommended) helps you stay on track.
Screen Early, Manage Well
Gestational diabetes affects a significant proportion of pregnant women in Singapore. The high prevalence is not a reflection of poor health habits, it is partly genetic and partly related to the physiological demands of pregnancy on women with a predisposition to insulin resistance.
The good news is that it is highly detectable and manageable. Universal screening at 24 to 28 weeks catches the vast majority of cases. Early detection allows for timely management, which reduces the risk of complications for both you and your baby.
If you are planning to become pregnant and have risk factors, discussing screening timing with your doctor before conception is worthwhile. If you are already pregnant and have not yet had your OGTT, discuss timing with your obstetrician or GP. Do not assume your risk is low unless you have been formally screened.
Your health, and your child's health, depend on early detection and appropriate management.
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Patient-first, Holistic, Dedicated Healthcare
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