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Gestational Diabetes: Symptoms, Diagnosis, and Management During Pregnancy

Gestational diabetes is a rise in blood sugar that occurs for the first time during pregnancy. It affects 7–14% of pregnant women and in most cases resolves after delivery. But while it's present, it requires attention and management. Without treatment, gestational diabetes raises the risk of complications for both mother and baby: a large baby, premature birth, pre-eclampsia, and low blood sugar in the newborn. The good news: with proper management, most women with gestational diabetes deliver healthy babies.

What is gestational diabetes and why does it develop

During pregnancy, the placenta produces hormones that help the baby grow. These hormones (progesterone, placental lactogen, cortisol) reduce the mother's cells' sensitivity to insulin — this is called insulin resistance. Normally, the pancreas compensates by producing more insulin. If it can't keep up, blood sugar rises. This is gestational diabetes.

Risk factors:

  • overweight or obesity before pregnancy (BMI 25 or above);
  • age over 25–30;
  • gestational diabetes in a previous pregnancy;
  • type 2 diabetes in close relatives;
  • polycystic ovary syndrome (PCOS);
  • a previous baby weighing more than 4 kg;
  • multiple pregnancy.

It's important to understand: gestational diabetes can develop without any risk factors. This is why screening is offered to all pregnant women.

Symptoms and diagnosis: the glucose tolerance test

Gestational diabetes often has no symptoms. Sometimes women notice:

  • increased thirst and frequent urination (though these are common in pregnancy anyway);
  • unusual fatigue;
  • blurred vision.

Because the symptoms are non-specific, the diagnosis is made only through blood tests.

The main diagnostic method is the oral glucose tolerance test (OGTT). It is performed at 24–28 weeks of pregnancy (earlier, in the first trimester, for those at high risk).

How the test works:

  1. A fasting blood glucose sample is taken.
  2. The woman drinks a solution containing 75 g of glucose.
  3. Blood is taken again after 1 hour and after 2 hours.

Gestational diabetes is diagnosed if at least one value exceeds the threshold:

  • fasting: 5.1 mmol/L or above;
  • 1 hour after the glucose load: 10.0 mmol/L or above;
  • 2 hours after the glucose load: 8.5 mmol/L or above.

If fasting glucose is 7.0 mmol/L or above, this is overt (manifest) diabetes, not gestational.

Blood sugar targets during pregnancy

Blood glucose targets during pregnancy are stricter than outside pregnancy. This is because even moderate rises in blood sugar affect the baby's development.

Target levels for gestational diabetes (self-monitoring with a glucometer):

  • fasting (before meals): below 5.1 mmol/L;
  • 1 hour after meals: below 7.0 mmol/L;
  • 2 hours after meals: below 6.7 mmol/L;
  • before bed: 5.1–7.1 mmol/L.

Glycated haemoglobin (HbA1c) is less informative during pregnancy than self-monitoring and is used as a supplementary measure.

Management and diet for gestational diabetes

In most cases (around 80%), gestational diabetes can be managed with diet and physical activity alone. Insulin is prescribed when diet is not sufficient.

Dietary principles:

  • Limit fast-acting carbohydrates: sugar, sugary drinks, white bread, white rice, mashed potato, pastries and sweets — all of these cause sharp rises in blood sugar.
  • Favour complex carbohydrates with a low glycaemic index: buckwheat, oats, brown rice, wholegrain bread, pulses.
  • Eat little and often: 3 main meals and 2–3 snacks. This helps avoid sharp blood sugar spikes.
  • Include adequate protein and fibre — these slow carbohydrate absorption.
  • Don't skip meals: long gaps between eating are harmful during pregnancy.

Physical activity:

Moderate physical activity (a 30-minute walk after meals, swimming, pregnancy exercise classes) lowers blood sugar and improves insulin sensitivity. Discuss appropriate activities with your doctor.

Self-monitoring:

With gestational diabetes, regular blood glucose self-monitoring is needed — typically 4–7 times a day (fasting and 1–2 hours after each meal). Keep a diary of your food intake and glucose readings — this helps your doctor adjust treatment.

Pre-eclampsia: a serious pregnancy complication

Pre-eclampsia is a pregnancy complication in which blood pressure rises and protein appears in the urine. It develops after 20 weeks of pregnancy and affects 2–8% of pregnant women. The risk of pre-eclampsia is higher with gestational diabetes.

Normal blood pressure during pregnancy: systolic (upper) below 140 mmHg, diastolic (lower) below 90 mmHg. A reading of 140/90 or above is a reason to see a doctor immediately.

Symptoms requiring urgent medical attention:

  • severe headache that doesn't go away;
  • visual disturbances (flashing lights, spots before the eyes);
  • pain in the upper abdomen (under the right ribs);
  • sudden swelling of the face, hands, or feet;
  • nausea and vomiting in the second half of pregnancy.

Pre-eclampsia can rapidly progress to eclampsia — a condition with seizures that is life-threatening for both mother and baby. If any of the above symptoms occur, call an ambulance immediately or go to a maternity unit.

If you're concerned about symptoms during pregnancy, describe them to our assistant to understand how urgently you need help.

Frequently asked questions

Will gestational diabetes go away after delivery?

In most cases, yes. Blood sugar levels normalise within a few weeks after delivery. However, women who have had gestational diabetes have a higher risk of developing type 2 diabetes in the future: around 50% develop it within 10 years. It's therefore important to check blood sugar 6–12 weeks after delivery and then every 1–3 years.

Does gestational diabetes affect the baby?

With poor control, yes. High blood sugar in the mother causes the baby to grow large (macrosomia, weight over 4 kg), which complicates delivery. After birth, the baby may have low blood sugar (hypoglycaemia), jaundice, or breathing difficulties. With good blood sugar control, the risks are significantly reduced.

Is insulin needed for gestational diabetes?

Around 20% of women with gestational diabetes need insulin — when diet and physical activity are not enough to achieve target glucose levels. Insulin is safe in pregnancy and does not cross the placenta to the baby. Oral glucose-lowering tablets are not used in pregnancy.

Can I eat fruit with gestational diabetes?

Fruit contains sugar (fructose) and can raise blood glucose. This doesn't mean it needs to be cut out completely. Fruits with a lower glycaemic index are preferable: apples, pears, cherries, berries. Avoid juices, bananas, grapes, and dates. Eat fruit in small portions and not on an empty stomach. Check your blood sugar response with a glucometer.

How is anaemia in pregnancy related to gestational diabetes?

Anaemia (low haemoglobin) and gestational diabetes are different conditions, but both need monitoring during pregnancy. Anaemia affects 20–40% of pregnant women, most often iron-deficiency anaemia. Symptoms: weakness, pallor, breathlessness, rapid heartbeat. Diagnosed by a full blood count. Treated with iron supplements prescribed by a doctor.

Is a caesarean section needed with gestational diabetes?

Gestational diabetes alone is not an indication for caesarean section. The method of delivery is decided individually, taking into account the baby's size, the mother's condition, and other factors. With good blood sugar control and a normally sized baby, vaginal delivery is possible.

Symptomatica is an informational reference service. Not a medical service; does not diagnose or prescribe treatment. For any symptoms, please consult a doctor.

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