The impact of ethnicity on pregnancy outcomes of gestational diabetes mellitus

Introduction. Gestational diabetes mellitus (GDM) refers to diabetes diagnosed in the second or third trimester of pregnancy that is not clearly overt diabetes prior to gestation. The prevalence of this condition significantly varies across different ethnic groups. In particular, Africans, Latinos, Asians and Pacific Islanders have the highest risk of developing GDM. Aim. The aim of this study was to evaluate the impact of ethnicity on pregnancy outcomes in GDM. Methods. A total of n=415 patients with GDM were enrolled, n = 152 of high-risk ethnicity (HR-GDM) and n = 263 of low-risk ethnicity (LR-GDM). Patients with age <18 years, pre-gestational diabetes, multiple pregnancy, psychiatric diseases and drug or alcohol abuse were excluded. A detailed medical history was obtained, including obstetrical information. Clinical and biochemical parameters were collected during pregnancy until delivery, as well as fetal ultrasound parameters and delivery data. Results. LR-GDM patients were significantly older than HR-GDM patients (35.7 ± 5.0 vs 31.6 ± 5.1 years, p<0.001) and had significantly higher third trimester BMI (30.5 ± 6.6 vs 28.9 ± 5.7 kg/m2, p=0.035). The prevalence of family history of type 2 diabetes, previous GDM and pluriparity were higher in HR-GDM group than in LR-GDM group. Values of fasting plasma glucose at oral glucose tolerance test (24-28 weeks) and glycosylated haemoglobin checked at third trimester of gestation were significantly higher in HR-GDM patients than LR-GDM patients (91.1 ± 11.1 vs 87.5 ± 11.7 mg/dl, p=0.01 and 5.5 ± 0.4 vs 5.3 ± 0.5 %, p=0.001, respectively). A greater proportion of HR-GDM patients required insulin therapy during gestation compared with LR-GDM patients (54.7% vs 35.7%, p<0.001). In multivariate analysis, HR-GDM was an independent predictor of insulin therapy (OR 2.19 [1.1-4.45] 95% CI, p=0.03). Gestational age at delivery was lower in HR-GDM group than in LR-GDM group (38.1 ± 1.9 vs 38.6 ± 1.7 weeks, p=0.026). Furthermore, HR-GDM group had higher prevalence of preterm delivery (28.1% vs 15.5%, p=0.03) and emergency Caesarean section compared with LR-GDM group (34% vs 19%, p=0.008). In multivariate analysis, HR-GDM was independently associated with preterm birth (OR 3.07 [1.50-6.30] 95% CI, p=0.002) and emergency Caesarean section (OR 2.41 [1.28-4.55] 95% CI, p=0.007). Conclusions. Relevant differences in pregnancy outcomes have emerged between patients belonging to different ethnic groups. In particular, high risk ethnicities had higher risk of pregnancy complications. In light of these findings, specific ethnic groups might benefit from more tailored prevention, intervention and follow-up strategies in the management of GDM.