Role of First-Trimester HbA1c as a Predictor of Adverse Obstetric Outcomes in a Multiethnic Cohort

Context Risk of obstetric complications increases linearly with rising maternal glycemia. Testing hemoglobin A1c (HbA1c) is an effective option to detect hyperglycemia, but its association with adverse pregnancy outcomes remains unclear. Emerging data sustain that an early HbA1c ≥5.9% could act as a pregnancy risk marker. Objective To determine, in a multiethnic cohort, whether an early ≥5.9% HbA1c could be useful to identify women without diabetes mellitus at increased pregnancy risk. Design and Setting A prospective study was conducted at Hospital del Mar, Barcelona, between April 2013 and September 2015. Patients and Intervention A total of 1631 pregnant women had an HbA1c measurement added to their first antenatal blood tests and were screened for gestational diabetes mellitus at 24 to 28 weeks' gestation. Outcome Measures Primary outcome was macrosomia. Secondary outcomes were preeclampsia, preterm birth, and cesarean section rate. Results A total of 1228 pregnancies were included for outcome analysis. Women with HbA1c ≥5.9% (n = 48) showed a higher rate of macrosomia (16.7% vs 5.9%, P = 0.008) and a tendency toward a higher rate of preeclampsia (9.32% vs 3.9%, P = 0.092). There were no statistically significant differences in other pregnancy outcomes. After adjusting for potential confounders, an HbA1c ≥5.9% was independently associated with a 3-fold increased risk of macrosomia (95% confidence interval, 1.127 to 8.603, P = 0.028) and preeclampsia (95% confidence interval, 1.086 to 11.532, P = 0.036). Conclusions In a multiethnic population, an early HbA1c ≥5.9% measurement identifies women at high risk for poorer pregnancy outcomes independently of gestational diabetes mellitus diagnosis later in pregnancy. Further studies are required to establish cutoff points adapted to each ethnic group and to assess whether early detection and treatment are of benefit.