Gestational Diabetes: Values, Risks, and Management in Pregnancy

Gestational diabetes is the most common form of metabolic complication of pregnancy, diagnosed in 5-10% of pregnant women in Italy (ISS, 2024). It is defined as an alteration in glucose tolerance that appears for the first time during pregnancy—typically in the second trimester—and in most cases resolves spontaneously after childbirth. However, spontaneous resolution does not mean an absence of consequences: women with a history of gestational diabetes have a 30-50% risk of developing type 2 diabetes within the following 10 years, and their children are more likely to develop obesity and metabolic alterations in adulthood.

Pregnancy itself is a state of physiological insulin resistance, mediated by placental hormones—placental lactogen, progesterone, cortisol—which progressively increase from the second trimester. This physiological insulin resistance serves to ensure an adequate supply of glucose to the growing fetus. In some women, the pancreas cannot compensate for this resistance with sufficient insulin production, leading to gestational hyperglycemia. Identifying and treating this condition early is essential for the health of both mother and newborn.

Normal blood glucose levels in pregnancy

Blood glucose targets during pregnancy are stricter than for the general population, because even small increases in glucose have significant effects on fetal development. The guidelines of the SID Diabetes and Pregnancy Study Group (2023) and NICE recommendations (2023) indicate:

It is sufficient for just one of the OGTT values to exceed the thresholds to diagnose gestational diabetes. Early diagnosis in the 1st trimester (fasting blood glucose ≥ 92 mg/dL) is considered "early" gestational diabetes and requires immediate management.

The OGTT test: when to do it and how it is performed

The OGTT (Oral Glucose Tolerance Test) is the standard diagnostic test. In Italy, it is recommended for all pregnant women between the 24th and 28th week of pregnancy and is performed free of charge under the national health service (code M02).

Here's how it's done step-by-step:

1. Fast for at least 8 hours (unsweetened water is allowed)
2. First fasting venous blood sample — baseline blood glucose
3. Consume a solution of 75 grams of anhydrous glucose dissolved in 200-250 ml of water, to be drunk in no more than 5 minutes
4. Second venous blood sample 1 hour after glucose load
5. Third venous blood sample 2 hours after glucose load
6. During the test: remain seated, do not walk, do not eat

Who should undergo early screening in the 1st trimester? Women with high risk factors: BMI ≥ 30 before pregnancy, gestational diabetes in previous pregnancies, first-degree family history of type 2 diabetes, PCOS (Polycystic Ovary Syndrome), glycosuria in the first urine test, or previous newborns with birth weight >4 kg.

Diet and management of gestational diabetes

Dietary therapy is the cornerstone of treatment and is sufficient on its own in 70-80% of cases, without the need for insulin. The nutritional plan must be personalized by a dietitian or diabetologist experienced in pregnancy, but the general principles are:

• Caloric distribution: maintain adequate caloric intake for pregnancy without excessive restrictions (risk of fetal ketosis)
• Carbohydrates: 40-45% of calories, with a preference for low glycemic index carbohydrates—legumes, whole grains, vegetables, fruit with skin
• Frequent small meals: 3 meals + 2-3 snacks distributed throughout the day to avoid blood glucose spikes
• Low GI breakfast: in the morning, insulin resistance is physiologically higher—prioritize proteins (eggs, Greek yogurt) and good fats over carbohydrates
• Fruit: moderate portions (150-200g at a time), never on an empty stomach, prefer whole fruits over juices
• Moderate physical activity: a 20-30 minute walk after main meals reduces postprandial blood glucose peak by 15-25% (ADA 2024)

If diet and physical activity are not sufficient to maintain values within target, insulin therapy is initiated—safe for mother and fetus, using insulins approved for pregnancy (NPH, detemir, lispro, aspart). Metformin is not the first choice in Italy during pregnancy.

Risks for mother and baby: what can happen without control

Untreated or poorly controlled gestational diabetes exposes to risks documented in international literature:

For the mother:

• Increased risk of C-section, especially in cases of fetal macrosomia
• Pre-eclampsia (hypertension with proteinuria in the 3rd trimester) — 30% increased risk
• Recurrent urinary tract infections (hyperglycemic environment promotes bacterial growth)
• Long-term risk of type 2 diabetes: 30-50% in the following 10 years

For the newborn:

• Fetal macrosomia (weight >4 kg): more frequent with uncontrolled GDM, causing delivery difficulties and increased risk of shoulder dystocia
• Neonatal hypoglycemia: in the first hours of life, due to excessive fetal insulin (the fetal pancreas responds to maternal hyperglycemia by producing extra insulin)
• Respiratory distress syndrome: related to induced prematurity or pulmonary immaturity from hyperinsulinism
• Increased risk of obesity, insulin resistance, and type 2 diabetes in childhood and adulthood (epigenetic effect of the intrauterine hyperglycemic environment)

With adequate glycemic control—the goal of GDM screening and management programs—these risks are drastically reduced, bringing outcomes closer to those of an uncomplicated pregnancy.

Postpartum follow-up: an appointment not to be forgotten

After childbirth, gestational diabetes resolves in the vast majority of cases. But follow-up is essential and often neglected:

• OGTT 75g between 6 and 12 weeks postpartum: to rule out persistence of diabetes and classify any alteration (IFG, IGT, diabetes)
• Fasting blood glucose or HbA1c every 1-3 years for the rest of life — the risk of type 2 diabetes remains elevated for decades
• Breastfeeding: recommended because it improves maternal insulin sensitivity and reduces the risk of childhood obesity
• Lifestyle: balanced diet and regular physical activity reduce the risk of progression to type 2 diabetes by 50-58% (Diabetes Prevention Program, NEJM 2002)

Frequently Asked Questions

Does gestational diabetes harm the baby in the womb?

If adequately controlled, gestational diabetes does not cause malformations (which are instead associated with pre-existing type 1 and 2 diabetes, especially if poorly controlled in the periconception period and 1st trimester). The main risks—macrosomia, neonatal hypoglycemia—are significantly reduced with glycemic control. Infants born to mothers with well-controlled GDM have perinatal outcomes comparable to those of non-diabetic pregnant women.

Can I breastfeed if I had gestational diabetes?

Not only is it possible, it is recommended. Breastfeeding improves maternal insulin sensitivity in the postpartum period and reduces the risk of developing type 2 diabetes. For the newborn, breast milk is always preferable to formula milk, regardless of a history of GDM. The World Health Organization recommends exclusive breastfeeding for the first 6 months of life.

If I had gestational diabetes, will it recur in my next pregnancy?

The probability of recurrence is high: 30-84% according to various studies, depending on the population and diagnostic criteria. It is essential to inform your gynecologist about your history of GDM at the beginning of a new pregnancy, to initiate screening immediately in the 1st trimester. Optimizing body weight and maintaining an active lifestyle between pregnancies significantly reduces this risk.

Home blood glucose monitoring is an integral part of gestational diabetes management. The Glucometer G1 Pro VitaeChek allows you to measure postprandial blood glucose in 5 seconds with MARD accuracy <5%, send data to the app, and generate a monthly report to share with your gynecologist or diabetologist. CE Class IIa certified · ISO 15197:2013 · 2-year warranty.