Ethnic Differences in Characteristics of Women Diagnosed with Early Gestational Diabetes: Findings from the TOBOGM Study

Objective: To compare the prevalence and clinical characteristics of early gestational diabetes (eGDM) and associated birth outcomes amongst women of different ethnic groups.

Research design and methods: This is a secondary analysis of an international, multicentre randomized controlled trial of treating eGDM among pregnant women with GDM risk factors enrolled <20 weeks' gestation. The diagnosis of GDM was made using WHO-2013 criteria. While Europids required at least one risk factor for recruitment, for others, ethnicity itself was a risk factor.

Results: Among women of Europid (n=1,567), South Asian (SA: n=971), East and South-East Asian (ESEA: n=498), Middle Eastern (ME: n=242) and Māori and Pasifika (MP: n=174) ethnicities; MP (26.4%) had the highest eGDM crude prevalence compared with Europid (20.3%), SA (24.7%), ESEA (22.3%) and ME (21.1%) (p<0.001). Compared with Europid, the highest eGDM adjusted odds ratio (aOR) was seen in SA (2.43 [95%CI 1.9-3.11]) and ESEA (aOR 2.28 [95%CI 1.68-3.08]); in late GDM, SA had the highest prevalence (20.4%: aOR 2.16 [95%CI 1.61-2.9]). Glucose patterns varied between ethnic groups and ESEA were predominantly diagnosed with eGDM through post-glucose load values, while all other ethnic groups were mainly diagnosed on fasting glucose values. There were no differences in the eGDM composite primary outcome or neonatal and pregnancy-related hypertension outcomes between the ethnic groups.

Conclusions: In women with risk factors, eGDM was most prevalent in SA and ESEA women, particularly identified by the post-glucose load samples. These findings suggest an early OGTT should particularly be performed in women from these ethnic groups.