Rates of gestational diabetes mellitus (GDM) are increasing in many areas of the world, according to research from Current Diabetes Reports. This condition poses risks during pregnancy and beyond to expectant parents as well as their children.
Guidelines from leading health organizations recommend screening for gestational diabetes in pregnancy between 24-28 weeks, yet emerging research suggests opportunities for earlier evaluation. Ultrasound remains an important tool to support early detection and inform clinical decision-making for both parental and fetal health.
Understanding Gestational Diabetes
Pregnancy and insulin resistance often go hand in hand. Gestational diabetes mellitus develops when pregnancy-related insulin resistance affects pancreatic function, resulting in abnormal blood glucose levels.
The current definition of GDM has evolved from previous characterizations, which did not distinguish between individuals with pregnancy-related glucose intolerance and those with preexisting diabetes that had gone undiagnosed until they were screened during pregnancy.
Now, however, the U.S. Preventive Services Task Force (USPSTF) and the American Diabetes Association have updated the GDM definition. Both organizations classify the condition as diabetes that develops during pregnancy rather than as undiagnosed diabetes arising before pregnancy.
Maternal and Fetal Risks
Guidance from the International Federation of Gynecology and Obstetrics (FIGO) describes the risks that diabetes poses to both parent and fetus. Intrauterine exposure to high blood sugar levels may increase the risk of shoulder dystocia and other birth traumas. It can also lead to hypoglycemia, polycythemia, cardiomyopathy, respiratory distress syndrome and an excessive buildup of bilirubin in fetal blood. Stillbirth is also more common in GDM pregnancies.
Pregnant patients who develop this condition face a high risk of preeclampsia, cesarean delivery and death, warns FIGO. They are more likely to hemorrhage and develop infections after delivery, and they are also more vulnerable to cardiac disorders and Type 2 diabetes with age.
The children of parents who had gestational diabetes are more prone to developing diabetes, high blood pressure and obesity themselves in adulthood.
Risk Factors for Gestational Diabetes
A 2018 practice bulletin from the American College of Obstetricians and Gynecologists (ACOG) reports that certain factors can increase an individual's risk for developing gestational diabetes, including:
- Obesity
- Older maternal age
- A previous gestational diabetes diagnosis
- Family history of diabetes
- Native American, Hispanic, South Asian, East Asian or Pacific Islander heritage
Patients with polycystic ovary syndrome or other conditions associated with increased diabetes risk or comorbidity may also be more vulnerable to developing gestational diabetes in pregnancy.
Screening Recommendations
Current ACOG practice guidelines recommend screening for gestational diabetes in pregnancy between 24-28 weeks of gestation. The 2021 Final Recommendation Statement from USPSTF advises a two-step process of a nonfasting 50g oral glucose challenge test during the same time period followed by an oral glucose tolerance test in patients meeting or exceeding the testing threshold.
However, factors such as obesity, a family history of Type 2 diabetes or fetal macrosomia during a previous pregnancy may indicate the need for assessment in the first or second trimester. USPSTF encourages clinicians to rely on their clinical judgment to determine the appropriate screening timeline for a patient's needs.
Ultrasound for Advanced Care
Ultrasound may help inform clinical decision-making for teams treating GDM patients. Ultrasonography has long been a trusted modality for estimating fetal weight, as the American College of Obstetricians and Gynecologists notes, although one retrospective cohort study suggests ultrasound may overestimate the size of the fetus.
Ultrasound can help uncover signs of fetal macrosomia late in the third trimester in patients with gestational diabetes. It is also critical for detecting congenital abnormalities, informing decision-making about the mode of delivery, monitoring placental changes and possibly predicting gestational diabetes at the early stages of pregnancy, notes a review from Maternal-Fetal Medicine.
Looking toward the future, advances in artificial intelligence may aid in the diagnosis of gestational diabetes. Cureus suggests that using an AI calculator in GDM screening could prove more convenient for patients and less costly to healthcare systems than current methods.
Gestational Diabetes in Diverse Patient Populations
Emerging research suggests high glucose may pose risks earlier in fetal development. Notably, Diabetes Care observes hyperglycemia-related fetal overgrowth beginning at 20 weeks — before patients were diagnosed with GDM and before the recommended diagnostic testing window. However, a 2018 paper in BMC Medicine suggests that GDM-associated changes in fetal growth may appear as early as 12–16 weeks gestation in some patient populations.
While the Diabetes Care investigation centered on largely white women, the BMC study group included 5,958 South Asian and 4,747 white patients in the U.K. Participants were administered oral glucose tolerance tests at 26-28 weeks. Fetuses were regularly measured via ultrasound. Gestational diabetes was diagnosed in 10.4 percent of South Asian patients and 4.4 percent of white patients, and GDM was associated with smaller fetal size in early pregnancy and larger fetal size from 24 weeks gestation onward.
Because changes in fetal growth may emerge before the screening period recommended by ACOG and USPSTF, the paper's authors suggest that South Asian patients may benefit from earlier screening and diagnosis. The authors further note that, as one possible step toward earlier assessment and treatment, the International Association of the Diabetes and Pregnancy Study Groups suggests providing a random fasting glucose assessment in the first prenatal visit.
BMC Medicine reports that fetal growth patterns differ considerably by ethnicity, potentially masking the detection of hyperglycemia-related changes in the developing fetus. Further research is needed to help clinicians understand the implications of gestational diabetes on fetal health and expand current standards of evaluation to reflect the needs of all patients.
Managing Gestational Diabetes
Initial treatment for gestational diabetes generally includes dietary changes, exercise, glucose monitoring and nutritional counseling and support. Routine, moderate exercise may prove particularly effective. A 2019 meta-analysis in BJOG reports a 24 percent decline in gestational diabetes in a study group that engaged in moderate exercise for 50-60 minutes twice weekly.
If initial interventions prove ineffective, ACOG recommends taking a multi-pronged approach to parental and fetal health management. Clinicians are advised to consider a combination of surveillance and prescription medications, such as oral hypoglycemic agents or insulin. Physicians should open a dialogue with patients about their delivery options and C-section risks.
Initiating treatment of gestational diabetes at 24 weeks gestation or later may improve fetal health, lowering the risk of large birth weight, birth injuries and NICU admissions finds the USPSTF. Similarly, treating pregnant patients for GDM at 24 weeks or later may lessen the risk of cesarean delivery and preterm birth, although findings for the latter are not statistically significant.
With appropriate monitoring and careful clinical guidance, patients with gestational diabetes and their children can receive more effective health monitoring than ever.
