Reference intervals for hemoglobin A1c (HbA1c) in healthy Mexican pregnant women: a cross-sectional study

BACKGROUND: The reference intervals for hemoglobin A1c (HbA1c) in pregnant Mexican women without diabetes are not well defined. The study aims to determine the reference intervals for HbA1c at each trimester in healthy Mexican pregnant women. METHODS: This cross-sectional study included healthy Mexican pregnant women in trimester 1 (T1), 6–13.6 weeks of gestation (WG), trimester 2 (T2), 14–27 WG, and trimester 3 (T3), ≥27–36 WG, with a maternal age > 18 years, and pregestational body mass index (BMI) ranging between 18.5–24.9 kg/m(2). Women with gestational diabetes mellitus, pregestational diabetes, anemia, a pregestational BMI < 18.5 or ≥ 25 kg/m(2), and any hematologic, hepatic, immunological, renal, or cardiac disease were excluded. HbA1c was measured using high-performance liquid chromatography based on the National Glycohemoglobin Standardization Program-certified PDQ Primus guidelines. The HbA1c reference intervals were calculated in terms of the 2.5th to the 97.5th percentiles. RESULTS: We analyzed the HbA1c values of 725 women (T1 n = 84, T2 n = 448, and T3 n = 193). The characteristics of the participants were expressed as mean ± standard deviation and included: maternal age (28.2 ± 6.7 years), pregestational weight (54.8 ± 5.9 Kg), pregestational BMI (22.2 ± 1.7 Kg/m(2)), and glucose values using a 75 g-2 h oral glucose tolerance test; fasting 4.5 ± 0.3 mmol/L (81.5 ± 5.5 mg/dL), 1 h 6.4 ± 1.5 mmol/L (115.3 ± 26.6 mg/dL), and 2 h 5.7 ± 1.1 mmol/L (103.5 ± 19.6 mg/dL). Reference intervals for HbA1c, expressed as median and 2.5th to 97.5th percentile for each trimester were: T1: 5.1 (4.5–5.6%), T2: 5.0 (4.4–5.5%), and T3: 5.1 (4.5–5.6%). CONCLUSIONS: The reference range of HbA1C in healthy Mexican pregnant women during pregnancy was 4.4% to 5.6%. We suggest as upper limits of HbA1c value ≤5.6%, 5.5%, and 5.7% for T1, T2, and T3, respectively among Mexican pregnant women.