What is gestational diabetes and why is everyone tested?
According to the standards of the Polish Gynaecological Society (PTG), gestational diabetes (GDM) is any degree of glucose intolerance that first appears or is first detected during pregnancy. It is distinguished from pregestational diabetes, which a woman already had before she became pregnant.
In a 2016 review, Katarzyna Cypryk of the Diabetes Clinic in Lodz describes how insulin resistance rises in pregnancy because levels of the pregnancy hormones oestrogen, progesterone and placental lactogen go up. In most women the body answers by making more insulin. In women with GDM that increase is too small, and blood glucose is too high. The paper estimates that gestational diabetes may affect over 10% of pregnant women, and links the rising diagnosis rate to later pregnancies, overweight and obesity, and to the new, lower diagnostic limits.
Glucose crosses the placenta, so a high level in the mother means a high level in the baby. According to the same paper, gestational diabetes raises the risk of excessive fetal growth (macrosomia), pregnancy-induced hypertension, caesarean birth and shoulder dystocia, and in newborns of low blood sugar and hyperbilirubinaemia, a raised bilirubin level that shows up as jaundice. In most cases GDM is mild, and once diagnosed it can be treated. The Polish Diabetes Society (PTD) advises aiming during treatment for the glucose values seen in healthy pregnant women.
That is why, according to Cypryk, all pregnant women should be tested for GDM, not only those at higher risk. The perinatal care standard (Dz.U. 2026 poz. 1140) schedules such a test in every pregnancy. You will find the full schedule of tests in our article on pregnancy tests covered by the NFZ.
When is the OGTT done in pregnancy?
The perinatal care standard sets two moments. At the first visit in pregnancy, up to 10 weeks, fasting glucose is measured, and women with risk factors for gestational diabetes have the OGTT already then. Between 24 and 28 weeks of pregnancy the test with 75 g of glucose is done with three measurements: fasting, 1 hour and 2 hours after drinking the solution.
The PTD recommendations from 2026 describe the same thing as an algorithm. All pregnant women should be assessed as early as possible after pregnancy is diagnosed. Women at risk have the OGTT straight away, other women have fasting glucose measured, and its result decides the next step:
| Fasting glucose at the first visit (woman without risk factors) | What next according to the PTD |
|---|---|
| below 92 mg/dl (5.1 mmol/l) | testing at 24-28 weeks of pregnancy with a single OGTT using 75 g of glucose |
| 92-125 mg/dl (5.1-6.9 mmol/l) | do the 75 g OGTT urgently, and refer to a reference centre if the results are abnormal |
| above 125 mg/dl (above 6.9 mmol/l) | repeat the fasting glucose measurement urgently |
Women at risk have the OGTT already at the first visit. If the result is normal, the test is repeated at 24-28 weeks. The PTD also stresses that a single fasting glucose in the first trimester between 92 and 125 mg/dl is not a basis for diagnosing hyperglycaemia in pregnancy. That needs an OGTT, done after proper preparation.
The test is free if you have it at a facility with an NFZ contract, because it is one of the tests in the standard.
How do you prepare for the OGTT?
The result depends on how the test is done, so the conditions are described in detail. Below they are given according to the PTD recommendations, the PTG standards and Cypryk's review. The sources differ slightly in the details, so if the laboratory gives you its own instructions, follow those.
- For at least 3 days before the test, eat normally and do not cut back on carbohydrates. The PTG says this means at least 150 g of carbohydrate a day with usual physical activity, and the PTD says the test is done without prior carbohydrate restriction.
- Come fasting. The PTD requires at least 8 hours without food or drink, except water. The PTG gives 8-14 hours since the last meal, Cypryk's review 8-12 hours, and the UK's NHS 8-10 hours. The first blood sample is taken before you drink the glucose.
- Come rested, ideally in the morning after a night's sleep. Cypryk recommends resting for 30 minutes before the test.
- Drink 75 g of glucose dissolved in 250-300 ml of water, within 5 minutes. The solution is very sweet. According to Cypryk you can add lemon juice or use a ready-made, factory-prepared solution.
- For 2 hours after drinking the solution, stay seated where the test is done. During that time do not eat, drink or smoke. Blood is taken 1 and 2 hours after you drink the glucose.
- The result must come from a laboratory. The PTD notes that glucose for diagnosis is measured in venous plasma, and that using a glucometer for diagnosis is not acceptable.
The PTG also lists situations in which the test is not done: during and within 72 hours after glucocorticoids given to speed up the baby's lung maturation, and during intravenous beta-mimetic therapy. If you are taking such medicines or start to feel unwell during the test, tell the staff. The whole test takes about 2 hours after you drink the solution, so bring something to read.
What are the OGTT limits in pregnancy?
Poland uses the IADPSG criteria from 2010 and the WHO criteria from 2013. The PTG updated its standards in 2014 after WHO changed the criteria, and the PTD gives the same values in its 2026 recommendations. Gestational diabetes is diagnosed when the result of one of the three measurements falls in the range in the table:
| Time of measurement | Gestational diabetes at a result of | The same result in mmol/l |
|---|---|---|
| Fasting | 92-125 mg/dl | 5.1-6.9 |
| After 1 hour | 180 mg/dl or more | 10.0 or more |
| After 2 hours | 153-199 mg/dl | 8.5-11.0 |
One abnormal result is enough for the diagnosis. The PTG writes that GDM is diagnosed if at least one value is abnormal, and the PTD that meeting at least one of the criteria in the table is enough.
Higher values mean a different category. The PTD classifies as diabetes in pregnancy (not gestational diabetes) a fasting glucose of 126 mg/dl (7.0 mmol/l) or more, a glucose at 2 hours of the OGTT of 200 mg/dl (11.1 mmol/l) or more, or a random glucose of 200 mg/dl or more with symptoms of hyperglycaemia. The PTG advises urgent referral to a reference centre if a repeated fasting result is 126 mg/dl or more. With a random glucose of 200 mg/dl or more, the PTG says a glucose load test is no longer done.
For comparison, the NHS describes a test in the UK with two blood samples: fasting and 2 hours after drinking the solution. In Poland the standard and the recommendations provide for three measurements.
Who is at higher risk of gestational diabetes?
In her review Cypryk lists these factors that raise the risk of GDM:
- pregnancy after the age of 35,
- a previous baby with a high birth weight (over 4000 g),
- a previous baby born with a malformation or an intrauterine death,
- high blood pressure,
- overweight or obesity,
- type 2 diabetes in the family,
- gestational diabetes in earlier pregnancies,
- having had several births,
- polycystic ovary syndrome (PCOS).
According to the PTG, women with a BMI of 30 or more, a history of GDM or any earlier carbohydrate intolerance should have the OGTT as early as possible, without waiting for week 24. The list of factors differs between countries. For example, the NHS lists age over 40, a BMI over 30, an earlier baby weighing 4.5 kg or more, gestational diabetes in the past, diabetes in a parent or sibling, South Asian, African, Caribbean or Middle Eastern family origin, and bariatric surgery.
Having no risk factors does not exempt you from the test. The test at 24-28 weeks applies to all pregnant women.
What happens after gestational diabetes is diagnosed?
Further care is led by a doctor, usually a diabetologist together with an obstetrician. The PTD recommends that women with diabetes in pregnancy are looked after by a diabetes and obstetric team experienced in this area. Treatment rests on diet and exercise and, where needed, insulin. The main elements according to the PTD 2026 recommendations and Cypryk's review:
- Self-monitoring of glucose. You measure your blood sugar with a glucometer after training from a nurse experienced in diabetes care. The number and timing of measurements depend on the severity of the disorder and on treatment. For women with gestational diabetes treated with insulin, the PTD recommends continuous glucose monitoring (CGM). At diagnosis it also recommends measuring HbA1c, but does not use it in routine monitoring of gestational diabetes.
- Target glucose values (PTD 2026): fasting and before meals 70-90 mg/dl (3.9-5.0 mmol/l), 1 hour after the start of a meal 110-140 mg/dl (6.1-7.8 mmol/l), 2 hours after 100-120 mg/dl (5.5-6.7 mmol/l), and between 2 and 4 a.m. 70-90 mg/dl.
- Diet. The PTD gives as a guide 40-50% carbohydrate (about 180 g a day), favouring low glycaemic index carbohydrates, 30% protein and 20-30% fat. It recommends regular mealtimes and a similar amount of carbohydrate at each meal, and Cypryk 5-6 meals spread evenly through the day. Artificial sweeteners are allowed, except saccharin. The diet is chosen individually, depending on body weight, height and activity.
- Do not go hungry. The PTD notes that a fasting urine ketone test can identify women who restrict carbohydrates too much to lower their sugar. Weight gain in pregnancy is also monitored.
- Exercise. If there are no contraindications, the PTD recommends moderate-intensity aerobic activity, and Cypryk walking, swimming and exercises of moderate intensity.
- Insulin, if diet and exercise are not enough. The PTD recommends it once the options of behavioural treatment are exhausted. According to Cypryk, normalising glucose requires insulin in 20-30% of women with GDM.
The PTD currently does not recommend oral medicines for treating diabetes in pregnancy. That includes metformin. The PTD writes that it crosses the placenta and that results of long-term follow-up of children are mixed, so insulin remains the drug of choice when diet fails. Exceptionally it allows metformin when a woman refuses insulin. In the UK the NHS writes of tablets or insulin, so recommendations differ between countries. The decision on treatment is always made by the doctor.
What is birth like with gestational diabetes?
The perinatal care standard counts gestational diabetes among the risk factors for perinatal complications, and at 33-37 weeks provides for a risk assessment with a recommended place of birth. Ask whoever is looking after your pregnancy to explain how your diabetes affects that assessment.
As to the mode and timing of birth, the 2014 PTG standards say that uncomplicated diabetes is not an indication for an operative birth or for ending the pregnancy early. A caesarean is considered when the baby is estimated to be too large, meaning over 4200 g in a woman of average height, or when the difference between abdominal and head circumference exceeds 4 cm. After 37 weeks, if excessive fetal weight is found, an attempt at induction can be considered. The NHS, on the other hand, says it is best to give birth before 41 weeks, with induction or a caesarean offered if labour has not started by itself. Earlier delivery may be advised when there are health concerns or sugar is not well controlled.
During labour the PTD recommends keeping glucose within 100-130 mg/dl (5.6-7.2 mmol/l), and the PTG measuring glucose every 1-2 hours. After the birth, ask how the hospital monitors the baby's glucose. According to Cypryk, newborns of mothers with GDM more often have low blood sugar (about 9% in the table in the paper) and hyperbilirubinaemia (about 29%). We write about newborn jaundice in a separate article.
What happens after birth: glucose checks and breastfeeding?
In most women glucose returns to normal after birth. Even so, the PTD and Cypryk advise that every woman is tested after gestational diabetes, because having had GDM raises the risk of overt diabetes in later years. The PTD puts such women in a group at high risk of diabetes and cardiovascular disease. The sources differ on the timing of checks:
| Source | First test after birth | Later follow-up |
|---|---|---|
| PTD 2026 | 75 g OGTT 6-12 weeks after birth | screening once a year, and an OGTT before another pregnancy |
| NHS | blood test for diabetes 6-13 weeks after birth | repeated every year if the result is normal |
| Cypryk 2016 | 75 g OGTT 6-12 weeks after birth | fasting glucose every 2-3 years, and an OGTT before another pregnancy |
| PTG 2014 | 75 g OGTT 6-12 weeks after birth (if glucose is normal in the puerperium) | fasting glucose once every 3 years |
The most recent of the Polish recommendations listed is the PTD from 2026, so checks after birth are based on it today. The PTD also notes that in pregnant women and in the postpartum period diabetes should not be diagnosed on the basis of HbA1c. After birth the need for insulin falls sharply, and most women can stop it.
According to the PTD and Cypryk, breastfeeding should be widely promoted and recommended to women with gestational diabetes, unless there are other contraindications. If you have trouble with feeding, read about pain when breastfeeding or book a lactation consultation.
What is the midwife's role in gestational diabetes?
Diagnosing and treating gestational diabetes is up to doctors, and decisions about therapeutic diet and insulin are made by the diabetes and obstetric team. According to the standard, a midwife can care for a pregnancy with a normal course, and when pathological symptoms appear she hands the patient over to a doctor. The OGTT result is entered in the pregnancy record, which you take to every visit.
A primary care (POZ) midwife provides free antenatal education and, after the birth, visits you at home during the postnatal (patronage) visits. She can then check how feeding is going and remind you about the glucose test 6-12 weeks after birth. A private midwife can support you at home in the postpartum period and with breastfeeding, but does not replace a diabetologist or dietitian. If you do not have a midwife yet, see how to choose and change your POZ midwife.
