Understanding Gestational Diabetes

Gestational diabetes is one of the most common pregnancy complications in the world. It’s also one of the most manageable — when you catch it early and treat it consistently. In 2024, the International Diabetes Federation estimated that approximately 23.3 million live births involved some form of high blood glucose during pregnancy. That’s roughly 1 in 6 pregnancies globally. Most women who develop gestational diabetes experience no noticeable symptoms. Doctors detect it through routine screening. That’s why attending all recommended antenatal appointments matters so much for both mother and baby.

Understanding gestational diabetes — what causes it, how doctors diagnose it, what risks it carries, and how to manage it — helps pregnant women and their partners engage actively in their care. It’s better than feeling managed by the condition instead. When blood sugar remains well controlled throughout pregnancy, the risks associated with gestational diabetes reduce substantially. This article covers everything you need to know. It’s based on the most current clinical guidelines, including the American Diabetes Association’s 2025 and 2026 Standards of Care and NHS guidance.

To understand how blood sugar management connects to metabolic health more broadly, read our guide on Prediabetes Explained: Can You Prevent Type 2 Diabetes?.

What Is Gestational Diabetes?

Gestational diabetes is high blood glucose that develops during pregnancy — most commonly in the second or third trimester. It occurs in women who did not have diabetes before becoming pregnant. It develops when pregnancy-related hormonal changes increase insulin resistance. The pancreas then cannot produce enough insulin to meet the increased demand.

During pregnancy, the placenta produces hormones including human placental lactogen, progesterone, and cortisol. These hormones progressively increase insulin resistance — a necessary adaptation that ensures the baby receives adequate glucose. In most pregnancies, the pancreas compensates by producing more insulin. In women who develop gestational diabetes, however, the pancreatic response is insufficient. Blood glucose rises above normal ranges and remains elevated if not actively managed.

A 2025 review published in PMC describes the pathophysiology in more detail. The condition involves reduced secretion and signalling of incretin hormones — particularly GLP-1 — which normally support insulin production after eating. Pro-inflammatory factors in the environment of pregnancy further impair insulin signalling pathways. The result is a metabolic situation distinct from type 1 or type 2 diabetes. It shares the core feature of inadequate blood glucose regulation.

Gestational diabetes resolves in most women after delivery. However, it significantly raises the long-term risk of developing type 2 diabetes. That’s one of the most important reasons to take it seriously even after pregnancy has ended.

Who Is at Risk of Gestational Diabetes?

Any pregnant woman can develop gestational diabetes, including those with no pre-existing risk factors. However, certain factors significantly increase the likelihood of developing the condition.

Risk factors for gestational diabetes

BMI above 30: excess body weight is one of the most significant risk factors. Adipose tissue releases fatty acids and inflammatory cytokines that worsen insulin resistance — compounding the pregnancy-related insulin resistance described above.
Previous gestational diabetes: women who develop gestational diabetes in one pregnancy have a 40 to 50 percent chance of developing it again in a later pregnancy. This is according to NHS guidelines.
Family history of type 2 diabetes: having a first-degree relative with type 2 diabetes significantly raises gestational diabetes risk. Shared genetic pathways affect both insulin secretion and sensitivity.
Ethnicity: women of South Asian, Black African, African-Caribbean, Middle Eastern, and East Asian descent face significantly higher gestational diabetes risk than white European women at the same BMI. NHS guidance recommends offering screening to these groups regardless of other risk factors.
Previous large baby: delivering a baby weighing 4.5kg or above in the past suggests that glucose metabolism may have been affected in that pregnancy. This holds true even if doctors did not formally diagnose gestational diabetes at the time.
Polycystic ovary syndrome: PCOS links to insulin resistance and carries significantly elevated gestational diabetes risk. Women with PCOS benefit from targeted screening and monitoring throughout pregnancy.
Age above 35: risk increases with maternal age, reflecting the progressive development of insulin resistance associated with ageing.

Gestational Diabetes Symptoms — Why Most Women Have None

Most women with gestational diabetes experience no noticeable symptoms — which is why routine screening is essential and not optional. When symptoms do occur, they are frequently mild and easy to attribute to normal pregnancy changes.

Symptoms that can indicate high blood glucose during pregnancy include:

increased thirst beyond what is typical for pregnancy
more frequent urination than usual for the stage of pregnancy
unusual fatigue — beyond the normal tiredness of pregnancy
blurred vision
recurrent thrush or urinary tract infections

None of these symptoms are specific to gestational diabetes. They overlap with many normal pregnancy experiences and with other common pregnancy conditions. Relying on symptoms to identify gestational diabetes means missing the majority of cases. Screening tests are the only reliable method of detection.

How Gestational Diabetes Is Diagnosed

In the UK, the NHS offers a glucose tolerance test to all pregnant women who have risk factors for gestational diabetes. This test typically happens at 24 to 28 weeks of pregnancy. Women with a previous gestational diabetes diagnosis receive testing earlier in pregnancy, often at 16 weeks. They receive a further test at 28 weeks if the first result is normal.

The oral glucose tolerance test

The OGTT is the standard diagnostic test for gestational diabetes. It requires overnight fasting. A fasting blood glucose reading comes first. The woman then drinks a glucose solution containing 75 grams of glucose. A second blood glucose reading follows two hours later.

In the UK, gestational diabetes is diagnosed if:

fasting plasma glucose is 5.6 mmol/L or above, or
two-hour plasma glucose is 7.8 mmol/L or above

These thresholds differ from the type 2 diabetes diagnostic thresholds. Doctors set gestational diabetes at lower glucose levels because even modest hyperglycaemia during pregnancy carries clinically meaningful risks to the developing baby.

When to request early screening

If you have significant risk factors — particularly previous gestational diabetes, BMI above 30, a family history of type 2 diabetes, or a relevant ethnicity — discuss early screening with your midwife or GP. Bring it up at your first antenatal appointment. Early identification allows earlier intervention, which significantly improves outcomes for both mother and baby.

Risks of Gestational Diabetes — for Mother and Baby

Understanding the risks of gestational diabetes is important for motivating consistent management. Those risks reduce substantially when blood glucose stays well controlled throughout pregnancy.

Risks to the baby

Macrosomia: when the mother’s blood glucose is elevated, excess glucose crosses the placenta to the baby. The baby’s pancreas produces extra insulin in response, which promotes fat storage and accelerated growth. Macrosomia — a baby weighing above 4.5kg at birth — significantly increases the risk of birth complications including shoulder dystocia.
Neonatal hypoglycaemia: after delivery, the baby’s pancreas keeps producing the elevated insulin levels it developed in response to high maternal glucose. Without the placental glucose supply, the baby’s blood sugar can drop significantly. This may require monitoring and, in some cases, glucose supplementation in the neonatal period.
Preterm birth: gestational diabetes raises the risk of preterm delivery before 37 weeks, both spontaneous and medically indicated due to complications.
Stillbirth: uncontrolled gestational diabetes in the third trimester significantly raises the risk of stillbirth. This is why women with gestational diabetes receive more frequent fetal monitoring, and why doctors may offer induction before term.
Long-term risks for the child: the ADA 2026 Standards of Care note that exposure to hyperglycaemia in utero raises risks for the child too — including obesity, hypertension, and type 2 diabetes later in life.

Risks to the mother

Pre-eclampsia: gestational diabetes raises the risk of pre-eclampsia, a pregnancy complication involving high blood pressure and organ involvement. It can be life-threatening if severe.
Caesarean section: macrosomia and other complications increase the likelihood of caesarean delivery.
Type 2 diabetes after pregnancy: women with gestational diabetes have a 50 percent risk of developing type 2 diabetes within five to ten years of the pregnancy. This is according to Diabetes UK.
Recurrence in future pregnancies: gestational diabetes recurs in 40 to 50 percent of subsequent pregnancies.

How to Manage Gestational Diabetes

The good news about gestational diabetes is that diet and physical activity can effectively manage the majority of cases. Only approximately 10 to 20 percent of women require medication in addition to lifestyle management. When blood glucose stays well controlled throughout pregnancy, the risks described above reduce substantially.

Blood glucose monitoring

Regular blood glucose monitoring is the foundation of gestational diabetes management. Most women test four times daily — fasting, and one to two hours after each main meal. The NHS targets for blood glucose in gestational diabetes are:

fasting (before breakfast): 5.3 mmol/L or below
one hour after meals: 7.8 mmol/L or below
two hours after meals: 6.4 mmol/L or below

Monitoring allows you to see how specific meals and activities affect your blood glucose — and to adjust your choices accordingly. Continuous glucose monitoring devices are increasingly available in gestational diabetes management. They reduce the need for finger-prick testing while giving more detailed information about blood glucose patterns.

Dietary management

Dietary change is the primary treatment for most women with gestational diabetes. The goal is not dramatic restriction but thoughtful carbohydrate management. This means choosing carbohydrates that raise blood glucose less steeply, spreading carbohydrate intake across the day to avoid large spikes, and balancing carbohydrate with protein and fat at each meal.

Key dietary principles supported by the ADA 2025 Standards of Care include:

Distribute carbohydrate across three meals and two to three snacks: smaller, more frequent meals reduce post-meal glucose spikes more effectively than eating the same carbohydrate amount in fewer large meals.
Choose lower glycaemic index carbohydrates: whole grains, legumes, non-starchy vegetables, and most fruits raise blood glucose more slowly than refined carbohydrates. This does not mean eliminating carbohydrates — it means choosing them thoughtfully.
Include protein at every meal: protein slows gastric emptying and reduces postprandial glucose rise. Including a protein source at each meal and snack is one of the most consistently effective strategies for managing postprandial blood glucose.
Limit refined carbohydrates and sugary drinks: white bread, white rice, pastries, fruit juices, and sugary drinks produce rapid and significant blood glucose spikes. These are the foods that most commonly require restriction in gestational diabetes management.
Work with a registered dietitian: personalised dietary advice from a dietitian familiar with gestational diabetes produces better blood glucose outcomes than general dietary guidance.

Physical activity

Regular moderate physical activity improves insulin sensitivity and helps the body use glucose more efficiently. Walking for 15 to 30 minutes after meals is particularly effective at reducing postprandial glucose spikes. Gentle walking, swimming, and pregnancy-specific exercise classes are all safe and beneficial during pregnancy for women without specific contraindications.

The ADA 2025 Standards of Care recommend that pregnant women aim for at least 150 minutes of moderate-intensity physical activity per week. This applies unless obstetric complications rule it out. Discuss your exercise plan with your midwife or obstetric team if you are unsure what is appropriate for your individual pregnancy.

Medication — when lifestyle management is insufficient

When diet and physical activity do not bring blood glucose within the recommended targets within one to two weeks — or when glucose is significantly elevated at diagnosis — doctors add medication to the management plan.

Metformin

Metformin is the most commonly used oral medication for gestational diabetes in the UK when lifestyle management alone is insufficient. It reduces glucose production in the liver and improves insulin sensitivity. Most women tolerate it well, and doctors consider it safe in pregnancy. Some women experience gastrointestinal side effects — nausea, diarrhoea, or stomach discomfort — particularly when starting treatment.

Insulin

Insulin is the most effective medication for controlling blood glucose in gestational diabetes. It does not cross the placenta and is considered the safest pharmacological option for the baby. Most women who require insulin use a combination of long-acting and short-acting insulin, adjusted according to blood glucose monitoring results.

After Gestational Diabetes: What Happens Next

For most women, gestational diabetes resolves after delivery. However, the postnatal period carries important responsibilities that many women don’t hear enough about.

The postnatal glucose test

The NHS recommends that all women diagnosed with gestational diabetes have a fasting plasma glucose or oral glucose tolerance test. This should happen six to thirteen weeks after delivery. This test checks whether glucose levels have returned to normal. This postnatal test finds type 2 diabetes in approximately 10 percent of women with gestational diabetes. A further proportion have prediabetes or impaired glucose tolerance. If your postnatal test is normal, doctors recommend annual fasting glucose testing for life, given the elevated lifetime risk of type 2 diabetes.

Reducing the long-term risk of type 2 diabetes

The lifestyle changes that manage gestational diabetes during pregnancy are exactly the same changes that reduce your long-term risk of type 2 diabetes afterward. Maintaining a healthy weight, eating a diet low in refined carbohydrates and processed food, exercising regularly, and attending annual glucose screening are the most evidence-supported steps you can take. They protect your long-term metabolic health after a gestational diabetes diagnosis.

For more on the relationship between prediabetes and type 2 diabetes prevention, read our article on Prediabetes Explained: Can You Prevent Type 2 Diabetes?.

The NHS guide to gestational diabetes provides comprehensive information on diagnosis, management, monitoring targets, medication options, and postnatal care for women in the UK.

Key Takeaways

Gestational diabetes affects approximately 1 in 6 pregnancies globally. An estimated 23.3 million live births involved high blood glucose during pregnancy in 2024, according to the International Diabetes Federation.
It develops when pregnancy hormones increase insulin resistance beyond the pancreas’s capacity to compensate — most commonly in the second or third trimester.
Most women with gestational diabetes have no noticeable symptoms. Routine screening at 24 to 28 weeks is the only reliable detection method.
Risks include macrosomia, neonatal hypoglycaemia, preterm birth, stillbirth, and pre-eclampsia for mother and baby. All of these reduce significantly when blood glucose stays well controlled.
Women with gestational diabetes have a 50 percent risk of developing type 2 diabetes within five to ten years of the pregnancy. This makes postnatal monitoring and lifestyle maintenance essential.
Diet and regular physical activity can manage the majority of gestational diabetes cases — particularly carbohydrate distribution, lower glycaemic index food choices, and protein at every meal.
All women with gestational diabetes should have a postnatal glucose test at six to thirteen weeks after delivery. Annual glucose screening should follow for life.

Final Thoughts

A gestational diabetes diagnosis can feel alarming, particularly in the midst of a pregnancy already filled with new information and new anxieties. The most important thing to understand is that this condition is highly manageable. The steps needed to manage it are not radical or extreme. They are the same steps that support good health in any context: eating thoughtfully, moving regularly, monitoring consistently, and attending the appointments your care team recommends.

When you manage gestational diabetes well during pregnancy, you protect both your baby’s immediate health and their long-term metabolic future. You also protect your own long-term health in a way that goes beyond the pregnancy itself. The habits you build during gestational diabetes management are among the most valuable health investments you can make — for both of you.

Attend your screening. Follow the plan. Ask every question you have. The information and the support are there — use them.

Medical Disclaimer: The information on this page is provided for educational and informational purposes only and is not intended as medical advice. It should not replace consultation with a qualified healthcare professional. For full details, please read our Disclaimer.