Gestational Diabetes Mellitus (GDM) is a condition that arises during pregnancy when the body cannot produce enough insulin to meet increased demands, leading to elevated blood glucose levels. Timely screening is essential because GDM often presents with subtle or no symptoms, yet it carries significant risks for both mother and baby if left unmanaged. While universal screening is recommended by organizations such as the American College of Obstetricians and Gynecologists (ACOG), recognizing specific symptoms can prompt earlier evaluation and potentially improve outcomes. This article details the common symptoms that may indicate a need for GDM screening, the risk factors that increase the likelihood of developing GDM, the screening process itself, and why early detection matters.

Common Symptoms That May Signal Gestational Diabetes

Many women with GDM experience no obvious symptoms, which is why routine screening between 24 and 28 weeks is standard. However, some women do develop signs that should raise suspicion. Below are the most frequently reported symptoms, along with explanations of why they occur.

Increased Thirst (Polydipsia) and Dry Mouth

Excessive thirst is a classic indicator of hyperglycemia. When blood sugar levels rise, the kidneys work harder to filter and absorb the excess glucose. If they cannot keep up, the extra glucose is excreted into urine, drawing water along with it. This leads to dehydration, which triggers a persistent feeling of thirst. Pregnant women who find themselves drinking far more than usual—especially if accompanied by frequent urination—should mention this to their healthcare provider.

Frequent Urination (Polyuria)

As blood glucose rises, the kidneys attempt to eliminate the surplus through urine. This increases urine output, resulting in more frequent trips to the bathroom. While increased urination is common in pregnancy due to hormonal changes and the growing uterus, a dramatic uptick—particularly if it interrupts sleep or seems excessive compared to earlier in the pregnancy—may be a sign of GDM.

Unusual Fatigue

Persistent tiredness that does not improve with rest can be a symptom of GDM. When cells cannot effectively use glucose for energy due to insulin resistance, the body’s tissues become energy-deprived. Additionally, the kidneys’ effort to excrete excess glucose places extra metabolic demands on the body. Fatigue is a common complaint in pregnancy, but severe or worsening fatigue warrants investigation.

Blurred Vision

Fluctuations in blood glucose levels can cause the lens of the eye to swell, altering its shape and leading to temporary blurred vision. This symptom may come and go. While blurry vision can also be caused by pregnancy-related changes in fluid retention or hormonal shifts, it is always worth discussing with a provider, as it may signal uncontrolled blood sugar.

Nausea and Recurrent Infections

Persistent nausea, especially beyond the first trimester, may be linked to high blood glucose. Elevated sugar levels can also weaken the immune system, making pregnant women more susceptible to infections such as urinary tract infections, yeast infections, or skin infections. Recurrent or stubborn infections should raise the question of underlying hyperglycemia.

Additional Symptoms to Monitor

Some women also report headaches, unexplained weight loss (despite a normal or increased appetite), or a general sense of being unwell. These symptoms are less specific but can accompany GDM, particularly when glucose levels are very high. Headaches may result from dehydration or blood sugar fluctuations.

It is important to note that many of these symptoms overlap with normal pregnancy complaints. The key is when they are more intense, persistent, or appear together. If you experience any combination of the above, especially if you have known risk factors, ask your provider about screening earlier than the standard schedule.

Risk Factors That Increase the Likelihood of GDM

Although any pregnant woman can develop GDM, certain factors significantly raise the risk. Knowing these can help determine if earlier or more frequent screening is appropriate.

Obesity or Overweight Before Pregnancy

A body mass index (BMI) of 30 or higher before pregnancy is a strong risk factor. Excess fat, particularly visceral fat, contributes to insulin resistance. Women who are overweight are urged to undergo screening early in pregnancy and again later if initial results are normal.

Previous Gestational Diabetes

Women who had GDM in a prior pregnancy are at high risk of recurrence. Studies show that up to 50% of women with a history of GDM will develop it again in a subsequent pregnancy. These women are typically screened early—often at the first prenatal visit—and retested later.

History of Polycystic Ovary Syndrome (PCOS)

PCOS is associated with insulin resistance even outside of pregnancy. Women with PCOS are more likely to have elevated blood sugar and may require closer monitoring throughout gestation.

Family History of Diabetes

A first-degree relative (parent or sibling) with type 2 diabetes indicates a genetic predisposition to insulin resistance and beta-cell dysfunction. This family history warrants careful screening.

Older Maternal Age

Maternal age over 35 is an independent risk factor. As women age, insulin sensitivity tends to decline, increasing the likelihood of developing GDM. The risk continues to rise with each additional year.

Additional Risk Factors

  • Previous delivery of a large baby (macrosomia, >9 pounds)
  • History of unexplained stillbirth or neonatal death
  • Ethnicity: higher prevalence in Hispanic, African American, Native American, South Asian, and Pacific Islander populations
  • Hypertension or preeclampsia in a prior pregnancy
  • Current pregnancy with multiple gestations (twins or more)

Women with one or more of these risk factors should have a conversation with their healthcare provider about the optimal screening plan for their pregnancy.

Screening Methods and Timing

When Is Screening Typically Done?

The American Diabetes Association (ADA) and ACOG recommend universal screening for GDM between 24 and 28 weeks of gestation in women without prior diabetes. For those with risk factors, an early screening (often at the first prenatal visit) may be performed to rule out pre-existing diabetes.

The Two-Step Approach

The most common method in the United States is the two-step process. First, a glucose challenge test is given: the patient drinks a 50-gram glucose solution, and blood glucose is measured one hour later. If the result is elevated (usually ≥130–140 mg/dL, depending on the laboratory’s threshold), a second test is performed.

The second test is the oral glucose tolerance test (OGTT). After fasting overnight, the patient drinks a 100-gram glucose solution. Blood samples are drawn at fasting, 1 hour, 2 hours, and 3 hours. GDM is diagnosed if two or more glucose values exceed certain cutoffs. This test provides a more precise picture of glucose metabolism.

The One-Step Approach

Some institutions use a one-step 75-gram OGTT, where blood glucose is measured at fasting, 1 hour, and 2 hours. This approach is endorsed by the International Association of Diabetes and Pregnancy Study Groups and is common outside the U.S. It simplifies the process but may identify more cases, leading to higher diagnosis rates.

Interpreting Results

Healthcare providers review glucose values against established thresholds. A diagnosis of GDM means the pregnancy requires careful management. An abnormal result is not a reason to panic—it is a prompt to begin interventions that can keep both mother and baby healthy.

Why Early Detection Matters

Untreated or poorly controlled GDM can lead to serious complications. Early detection allows for timely lifestyle changes and, if needed, medical therapy, which dramatically reduces risks.

Risks to the Baby

  • Macrosomia: Excess glucose crossing the placenta causes the baby to grow too large, increasing the risk of shoulder dystocia, birth injuries, and need for cesarean delivery.
  • Neonatal hypoglycemia: After birth, the baby’s pancreas continues to produce high insulin levels, causing a drop in blood sugar that can be dangerous if not monitored.
  • Preterm birth: High glucose levels can trigger early labor or require early delivery due to fetal distress or maternal complications.
  • Respiratory distress syndrome: Babies born to mothers with GDM may have immature lungs.
  • Long-term risks: Offspring have a higher likelihood of developing obesity, type 2 diabetes, and metabolic syndrome later in life.

Risks to the Mother

  • Preeclampsia: GDM increases the risk of developing high blood pressure and protein in the urine during pregnancy, a condition called preeclampsia that can be life-threatening.
  • Increased risk of cesarean delivery: Due to large baby size or complications during labor.
  • Future diabetes: Women who have had GDM have a 50% chance of developing type 2 diabetes within 5 to 10 years after pregnancy.
  • Recurrence in subsequent pregnancies: GDM often returns.

Screening and treatment significantly lower these risks. According to the Centers for Disease Control and Prevention, managing GDM can prevent most complications.

Managing GDM After Diagnosis

If you are diagnosed with GDM, your healthcare team will help you develop a personalized plan. The foundation involves:

Blood Glucose Monitoring

You will be taught to check your blood sugar at home, typically before meals and one hour after meals. Keeping a log helps identify patterns and adjust treatment.

Dietary Changes

A registered dietitian can create a meal plan that controls carbohydrates while ensuring adequate nutrition for you and your baby. Focus on complex carbohydrates, lean protein, healthy fats, and plenty of vegetables. Spreading food intake across three meals and two to three snacks helps maintain stable glucose levels.

Physical Activity

Moderate exercise, such as walking, swimming, or prenatal yoga, improves insulin sensitivity. Aim for at least 30 minutes of moderate activity most days, unless contraindicated by your pregnancy.

Medication If Needed

If diet and exercise are not enough to keep blood sugar in target ranges, medication may be needed. Insulin is the most common and safest option during pregnancy. Some oral medications, like metformin, are used in certain cases, but insulin remains the gold standard.

Monitoring the Baby

Your provider may recommend extra ultrasounds to track fetal growth and amniotic fluid levels. Non-stress tests may also be used to assess the baby’s well-being in the third trimester.

When to Speak to Your Healthcare Provider

If you experience any of the symptoms mentioned in this article, or if you have risk factors for GDM, do not wait for the routine screening window. Contact your obstetrician or midwife to discuss your concerns. Early detection and intervention are the most effective ways to protect your health and your baby’s health. For additional authoritative information, refer to the ACOG patient FAQ on gestational diabetes and the National Institute of Diabetes and Digestive and Kidney Diseases.

Conclusion

Recognizing the symptoms of GDM is a valuable step, but it is equally important to remember that many women have no symptoms at all. Universal screening between 24 and 28 weeks remains the standard of care. However, being aware of the warning signs—such as excessive thirst, frequent urination, fatigue, blurred vision, or recurrent infections—can prompt earlier evaluation, especially when combined with known risk factors. With proper management, the vast majority of women with GDM go on to have healthy pregnancies and babies. If you have any concerns, talk to your healthcare provider today. Proactive care makes all the difference.