Elevated blood glucose levels during pregnancy represent one of the most common metabolic challenges, requiring special attention and timely screening. Since gestational diabetes often lacks clinical symptoms in its early stages, its early detection and proper management play a crucial role in ensuring the health of both mother and fetus.
What biological mechanisms underlie gestational diabetes, who falls into the high-risk group, how diagnostic tests are conducted, what complications may develop for the mother and fetus, and what the modern management protocol includes — clinical professor and obstetrician-gynecologist Maka Chikovani spoke with us on these and other important issues.
What is gestational diabetes and what is its biological mechanism?
Gestational diabetes is a condition that develops from the second half of the second trimester of pregnancy (after 24–26 weeks) and is characterized by elevated blood glucose levels. Its development is based on the secretion of so-called counter-regulatory (anti-insulin) hormones produced during pregnancy. These hormones have an effect opposing insulin, and if the pancreas cannot cope with the insulin resistance that arises during pregnancy — meaning it cannot produce an adequate amount of insulin — gestational diabetes develops. Globally, the prevalence of gestational diabetes is 16%, with the majority of cases occurring in developing countries.
How to distinguish pre-existing diabetes from gestational diabetes?
In general, elevated blood glucose during pregnancy is referred to as gestational diabetes. However, if elevated values are detected either before pregnancy or during the first half of pregnancy, it refers to pregestational (pre-existing) diabetes. A certain proportion of patients are aware of having diabetes based on previous evaluations, while others are not, since diabetes in its early stages may not present any pronounced symptoms.
Classic symptoms of hyperglycemia (including polyuria – frequent urination, polydipsia – excessive thirst, nocturia – nighttime urination, blurred vision, and weight loss) are often noticed only retrospectively, after elevated glucose levels have already been established. Frequent urination and nighttime urination are common symptoms of the first trimester of pregnancy, making it difficult to diagnose diabetes during this period based solely on symptoms. That is why, to rule out pre-existing diabetes and identify high-risk patients, a glycated hemoglobin (HbA1c) test is recommended in the very first trimester. It indicates whether glucose levels were elevated over the past 3 months.
Which diagnostic tools are recommended for detecting gestational diabetes?
Since gestational diabetes in the vast majority of cases (especially in early stages) presents no clinical symptoms, screening in pregnant women is of particular importance. At the very first visit (in the first trimester), a glycated hemoglobin (HbA1c) test is performed to rule out pre-existing diabetes (this test is not covered by the state antenatal program).
Standardly, gestational diabetes screening under the state antenatal program is performed at 26 weeks. During screening, the pregnant woman is loaded with 50 grams of glucose — this is called the “Glucose Challenge Test.” Blood glucose is checked 1 hour after ingestion to evaluate how insulin worked. The blood glucose level should not equal or exceed 135 mg/dL. The Glucose Challenge Test is a highly sensitive screening test with relatively lower specificity. This means it will not miss a patient with gestational diabetes, though it may yield false-positive results.
Therefore, if the result of the 50-gram test is 135 mg/dL or higher, the patient proceeds to the next diagnostic evaluation — the 100-gram “Oral Glucose Tolerance Test.” During this test, the patient is given 100 grams of glucose, and blood glucose levels are checked 4 times: fasting (should be less than 95 mg/dL), at 1 hour (less than 180 mg/dL), at 2 hours (less than 155 mg/dL), and at 3 hours (less than 140 mg/dL). If two or more of the 4 values are abnormal, a diagnosis of gestational diabetes is established, whereas a single elevated value is considered impaired glucose tolerance and requires different monitoring.
Who needs a more thorough evaluation?
Women with a medical history of impaired glucose values or gestational diabetes in a previous pregnancy; a family history of diabetes in first- and second-degree relatives (parents, siblings, children, grandparents); overweight or obesity (body mass index – BMI higher than normal); a history of delivering a infant weighing over 4 kg (macrosomia); or glucose detected in a routine urinalysis at the very first visit (glucosuria). Glucose should not be present in the urine during the first trimester, as renal filtration changes begin later, and its appearance serves as grounds for early testing. Such patients are advised to monitor glucose levels at home using a glucometer, adjust their diet, and, if necessary, are referred to an endocrinologist.
What are the risk factors for developing gestational diabetes?
The main risk factors for developing gestational diabetes are: overweight and obesity, age (35 years and older), genetic predisposition – presence of diabetes in first- and second-degree relatives, polycystic ovary syndrome (recently referred to as polyendocrine metabolic ovary syndrome), and multifetal pregnancy. Additionally, the risk of developing gestational diabetes is higher if a woman gained excessive weight during the first half of pregnancy and consumes large amounts of carbohydrates.
What preventive measures exist to avoid gestational diabetes?
Some of the aforementioned risks are modifiable and lifestyle-dependent. The ideal approach is preconception planning, weight loss, and normalization of glucose levels prior to pregnancy. During pregnancy, risks are significantly reduced by proper nutrition (carbohydrate restriction and intake of protein-rich foods) and physical activity. If a woman did not exercise previously, strenuous physical exertion is unnecessary; even 30-40 minutes of purposeful walking is acceptable and sufficient.
What impact does gestational diabetes have on maternal and fetal health, and does its presence increase the need for a C-section?
The main complication of gestational diabetes is a large-for-gestational-age fetus — macrosomia (4 – 4.5 kg and above), which increases the risk of birth trauma for both mother and fetus. Furthermore, poorly managed diabetes is associated with adverse pregnancy outcomes (stillbirth, perinatal mortality) and increases the risk of developing preeclampsia (blood pressure elevation to 140/90 mmHg or higher after 22 weeks of pregnancy). All these factors, both fetal macrosomia and the development of preeclampsia, significantly increase the necessity of performing a C-section, the rate of which is already quite high in Georgia even without gestational diabetes.
For the fetus, there are both immediate and long-term complications: intrauterinely, the risk of chronic hypoxia and fetal distress increases, while at birth, such infants face the risk of developing neonatal hypoglycemia.
As for long-term complications: after birth, these children face an increased risk of developing type 1 and type 2 diabetes, obesity, metabolic syndromes, and autism spectrum disorders in the future. Additionally, excessive carbohydrate consumption by the mother during intrauterine life may contribute to the future development of polycystic ovary syndrome in female offspring.
On the mother’s side, diabetes resolves in most cases after delivery; however, the risk of developing type 2 diabetes mellitus and cardiovascular diseases remains high in the future. Therefore, repeat monitoring of blood glucose levels at the postpartum visit is essential.
To briefly summarize, what is the first line of management for gestational diabetes, and when does medical treatment become necessary for the patient?
The first-line management of gestational diabetes includes: dietary therapy — rational carbohydrate restriction (as certain carbohydrates are essential for a pregnant woman) and consumption of protein-rich foods, physical activity — dosed cardio exercise, and glucose self-monitoring — periodic checking of blood glucose levels with a glucometer.
When blood glucose levels remain normal through balanced diet and physical activity, pharmacological therapy is not required. However, if elevated glucose is recorded in 30% of daily glucometer measurements (one-third of readings) or if the patient, for various reasons, cannot adhere to dietary recommendations, appropriate treatment (metformin-group drugs or insulin therapy) is prescribed by an endocrinologist.
