History and exam
Key diagnostic factors
common
presence of risk factors
Key risk factors include advanced maternal age (>40 years), elevated BMI, polycystic ovarian syndrome, family origin in an area with high prevalence of diabetes mellitus, and family history of diabetes.
abnormal oral glucose tolerance test
Gestational diabetes mellitus diagnosis is based on an abnormal screening oral glucose tolerance test at 24-28 weeks' gestation.
Testing strategies adopt either a one-step method using the 75-g oral glucose tolerance test or a two-step method using a 50-g (nonfasting) glucose load to screen, followed by a 100-g oral glucose tolerance test for those who screen positive.
Other diagnostic factors
uncommon
polyuria
May be a sign of overt hyperglycemia. Suggests uncontrolled diabetes and urgent need for plasma glucose testing. Unusual in GDM and more common in individuals with preexisting diabetes.
polydipsia
May be a sign of overt hyperglycemia. Suggests uncontrolled diabetes and urgent need for plasma glucose testing. Unusual in GDM and more common in individuals with preexisting diabetes
fetal macrosomia
Prior birth of an infant >4000 g may be due to unrecognized gestational diabetes mellitus.
Risk factors
strong
advanced maternal age (>40 years)
Risk of gestational diabetes mellitus (GDM) increases slowly until age 40 years, at which point risk accelerates and likelihood of GDM is more than doubled to tripled.[27][28] This relationship between age and GDM mirrors the increased prevalence of type 2 diabetes with aging and is thought to arise from decreasing pancreatic beta-cell reserve in the setting of increased insulin resistance.[14]
elevated BMI
polycystic ovarian syndrome (PCOS)
PCOS is associated with insulin resistance and obesity.[14] This syndrome more than doubles gestational diabetes mellitus (GDM) risk.[16] It is also associated with type 2 diabetes; thus even in the absence of pregnancy, screening for glucose and lipid abnormalities should be considered in women with POCE.[17]
A meta-analysis of studies comparing pregnancy outcomes between women with diagnosed PCOS and those without the condition found statistically significant increased rates of GDM, pregnancy-induced hypertension, preeclampsia, preterm delivery, and small-for-gestational-age infants in women with PCOS.[30]
ancestry
Family origin in an area with high prevalence of diabetes mellitus, including South Asian (specifically women whose country of family origin is India, Pakistan, or Bangladesh), Black Caribbean, and Middle Eastern (specifically women whose country of family origin is Saudi Arabia, UAE, Iraq, Jordan, Syria, Oman, Qatar, Kuwait, Lebanon, or Egypt) is associated with increased risk of gestational diabetes mellitus (GDM).[14][19][27][31]
In one US study, GDM prevalence in a California population varied from approximately 4.5% in non-Hispanic white and African-American women to 10.2% in Asian women.[3] Notably, Asian-American women were at increased risk even at relatively low BMI.[3]
Environmental and social factors, including systemic racism, are likely contributors to population-level disparities in both diabetes prevalence and disease outcome.[18]
family history of type 2 diabetes mellitus
previous gestational diabetes
Gestational diabetes mellitus recurs in as many as 80% of subsequent pregnancies.[22]
previous macrosomic baby
Having a previous baby that weighed ≥4.5 kg is associated with a significantly higher risk of being diagnosed with gestational diabetes mellitus in a subsequent pregnancy (OR 5.59, 95% CI 2.68 to 11.7).[19]
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