Introduction
Gestational Diabetes Mellitus_Disease Background 1
Gestational diabetes mellitus (GDM) is any degree of glucose intolerance with onset or first recognition during pregnancy. It is diabetes that is first diagnosed in the second or third trimester of pregnancy that has not been a pre-existing type 1 or 2 diabetes. Hyperglycemia in pregnancy may be suggested by the presence of glycosuria, a fetus that is large for date, or polyhydramnios.
Overt diabetes mellitus (DM), a diabetes diagnosed in the first trimester of pregnancy, is classified as pre-existing gestational diabetes. Overt DM may be found in women presenting with risk factors for type 2 diabetes during the first prenatal visit (before 13 weeks of gestation). The risk for the development of postpartum overt type 2 diabetes is increased in patients with gestational diabetes mellitus compared to those with normoglycemic pregnancies.
Epidemiology
Gestational diabetes mellitus is a common pregnancy complication globally, affecting approximately 1 in 6 live births, according to data from the International Diabetes Federation. The overall estimated prevalence of gestational diabetes mellitus in Europe stands at 10.9%, while, in the United States, roughly 7% of all pregnancies are complicated by some form of diabetes, with GDM accounting for 86% of those cases. The prevalence of gestational diabetes mellitus appears to be high in South Asian and Southeast Asian women compared to African-American, Caucasian, and Hispanic women; prevalence rates are 3-21.2% in women with GDM who were born in Asian countries. The rates of fetal macrosomia are lower in Southeast Asian women than in American Caucasian women. Asian women with gestational diabetes mellitus have a higher incidence of abnormal postpartum glucose tolerance tests, and the risk of developing type 2 DM in the future is higher than in Anglo-European women.
A retrospective study of 138,530 Japanese women demonstrated that those over 40 carried a 15.1% relative risk for gestational diabetes mellitus, whereas separate epidemiological data noted that the peak age-specific prevalence is seen among a slightly younger cohort of women aged 30 to 34 years.
Pathophysiology
During pregnancy, human placental lactogen causes maternal insulin resistance, which healthy pregnancies counteract by multiplying pancreatic β-cells to boost insulin production. Gestational diabetes develops when this metabolic compensation fails, a breakdown driven either by pancreatic β-cell dysfunction, where insulin secretion is delayed or insufficient, or by early maternal obesity, where elevated free fatty acids block glucose uptake and force the liver to overproduce sugar.
Risk Factors
Gestational Diabetes Mellitus_Disease Background 2
Risk factors for type 2 diabetes mellitus (DM) include overweight or obesity, high-risk ethnicity (eg African-American, Latino, Native American, Asian, or Pacific Islander), physical inactivity, history of GDM with hypertension, history of cardiovascular disease (CVD), polyendocrine metabolic ovarian syndrome (PMOS), acanthosis nigricans, high-density lipoprotein (HDL) cholesterol level of 0.90 mmol/L (<35 mg/dL) and/or triglyceride level of 2.82 mmol/L (>250 mg/dL), with a previous test result that showed A1c ≥5.7%, impaired glucose tolerance or impaired fasting glucose, DM in first-degree relatives, and glycosuria at the first prenatal visit.