WHAT IS GESTATIONAL DIABETES?

Gestational diabetes mellitus (GDM) is a type of diabetes that develops during pregnancy and as a consequence of pregnancy, in contrast to pre-existing diabetes in pregnant women.¹ During the late second trimester and early third trimester, insulin-mediated glucose uptake is greatly reduced. In healthy women, this insulin insensitivity is counteracted by a corresponding increase in insulin production to maintain blood sugar levels.² GDM results when the body’s insulin secretion is insufficient to meet its needs.³ In many cases, women who develop GDM had asymptomatic insulin resistance and b-cell defects prior to conception.^4,5 These defects only become clinically manifested as a result of pregnancy-induced insulin resistance.⁶ Usually, GDM is diagnosed during the late second trimester and resolves at giving birth.¹

WHAT ARE THE RECENT TRENDS IN GESTATIONAL DIABETES?

Every year, approximately 2% to 10% of every pregnancy in the U.S. is affected by GDM.⁷ In an analysis of 12.6 million first-time mothers in the U.S. between the ages of 15 to 44 who gave birth between 2011 to 2019, the rate of GDM increased from 47.6 to 63.5 per 1000 live births, amounting to an average annual increase of 3.7%.⁸ The increase was observed across all racial and ethnic groups. The study noted that the trend paralleled the rise in the prevalence of obesity, physical inactivity, and poor diet quality. Advanced maternal age, associated with an increased risk of GDM, may have contributed to the observed trend. However, only a modest increase (<2 years) in maternal age at delivery was observed over the past decade.⁹

WHAT ARE THE RISK FACTORS FOR DEVELOPING GESTATIONAL DIABETES?

There are several clinical, pregnancy-related, and lifestyle factors that are associated with an increased risk of developing GDM.^6,10,11

 
Clinical Risk Factors

• Overweight (body mass index (BMI) >25 kg/m²) or obesity (BMI >30 kg/m²)
• Advanced maternal age
• Family history of T2D
• History of GDM or glucose intolerance
• Polycystic ovary syndrome
• Current glycosuria
• Certain racial/ethnic background (Hispanic, Native American, South or East Asian, or Pacific Islander)
• Other genetic factors

Pregnancy-Related Risk Factors

• Previous infant with macrosomia (fetal overgrowth)
• Male fetus
• Number of previous pregnancies (>20 weeks of gestation)
• Multiple pregnancy

 
Lifestyle Risk Factors

• Poor dietary habits
• Physical inactivity
• Cigarette smoking

 
WHY IS IT IMPORTANT TO MANAGE GESTATIONAL DIABETES?

If left unmanaged, GDM can result in serious short-term and long-term health consequences for both the mother and the child.⁶

 
Short-Term Complications – GDM is associated with complications such as pre-eclampsia (high blood pressure and protein in urine), fetal overgrowth, operative delivery, birth canal lacerations, shoulder dystocia (baby’s shoulder(s) getting stuck during delivery), polyhydramnios (too much amniotic fluid), neonatal hypoglycemia (low blood sugar for the infant), jaundice, and even death of the fetus in rare cases.

Long-Term Complications – A meta-analysis of 20 cohort studies found that women with GDM are at a sevenfold increased risk of developing subsequent T2D when compared to women with normoglycemic pregnancies. They are also at a greater risk for developing metabolic syndrome, cardiovascular, retinal, liver, and kidney disease. Additionally, children of women with GDM are at an increased risk of developing insulin resistance, pre-diabetes, diabetes, metabolic syndrome, and being overweight.

 
HOW IS GESTATIONAL DIABETES MANAGED?
 
Even though untreated GDM can have serious maternal and fetal consequences, GDM is generally easily managed through lifestyle changes, pharmacotherapy, and proper blood-glucose monitoring.

Lifestyle Management – Nearly 85% of patients with GDM can manage their illness and achieve target glucose levels through lifestyle changes (diet, physical activity, weight control) alone.^12,13 The American Diabetes Association (ADA) recommends consulting a dietician to follow a personalized diet that provides adequate nutrition for the pregnancy yet restricts carbohydrate intake to 35% to 40% of daily calories.^14,15 For those with obesity, the ADA suggests reducing daily caloric intake by 30% to 33%.¹⁵ Additionally, as long as there are no contraindications, they are encouraged to engage in pregnancy-safe physical activities throughout pregnancy. Weight loss is generally not recommended during pregnancy. Rather, appropriate and healthy weight gain should be encouraged. The Institute of Medicine recommends 25-35 lb weight gain for those with normal BMI (19.8-26.0 kg/m²) and 15-25 lb or <15 lb weight gain for those who are overweight or obese, respectively.¹⁶

Pharmacotherapy – Pharmacotherapy can be considered in patients whose glucose levels cannot adequately be controlled through lifestyle changes.¹⁵ It can also be considered when fetal overgrowth is noted on sonogram.²⁰ Insulin therapy is the favored pharmacological agent, as it is both effective and safe for the fetus.¹⁵ Oral hypoglycemic agents are usually not recommended due to potential side effects, but metformin and glyburide may alternatively be used.^21,22

Blood Glucose Monitoring – Alongside lifestyle and pharmacological management, patients with GDM should monitor their blood glucose levels through either intermittent self-monitoring or continuous glucose monitoring.¹⁷ For those who self-monitor, they are recommended to check their blood glucose levels before breakfast (ie, fasting glucose level) and at one or two hours after beginning each meal (ie, postprandial glucose level). The ADA gives the following recommendations as the upper limits for glucose levels:^18,19

• Fasting Blood Glucose Concentration: <95 mg/dL
• One-Hour Postprandial Blood Glucose Concentration: <140 mg/dL
• Two-Hour Postprandial Blood Glucose Concentration: <120 mg/dL