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Objectives: This study aimed to define trimester-specific hemoglobin A1c (A1c) reference intervals among healthy South Asian pregnant women. Methods: In this restrospective study,1357 pregnant women without diabetes, gestational diabetes, gestational hypertension, anemia, β-thalassemia, or systemic diseases were included. They had term delivery of babies having weight appropriate for gestational age. A1c (using high performance liquid chromatography, meeting the National Glycohemoglobin Standardization Program and International Federation of Clinical Chemistry standards), hemoglobin, and RBC indices were estimated at the first antenatal visit. The A1c levels were calculated in terms of non-parametric 2.5 and 97.5 percentiles for women in first (T1), second (T2), and third (T3) trimester groups. The control group included 67 healthy non-pregnant women. Statistical tests were used to obtain the normal the normal reference values for the HbA1c . and the tests were considered significant when p value <0.05. Results: The median HbA1c (2.5 to 97.5 percentiles) was lower among the pregnant women; 4.8 (4-5.5) % or 32 (20-39) mmol/mol than in the non pregnant women; 5.1 (4-5.7) % or 29 (20-37) mmol/mol ( p <0.001). These were 4.9 (4.1-5.5) % or 30 (21-37) mmol/mol, 4.8 (4-5.3) % or 29 (20-34) mmol/mol, and 4.8 (3.9-5.6) % or 29 (19-38) mmol/mol for the T1, T2 and T3 groups, respectively; p-values:T1 vs T2=<0.001, T1 vs T3= 0.002, T2 vs T3= 0.111, T1 vs non pregnant group = <0.001. Conclusions: Compared to normal non pregnant women, the A1c was lower in normal pregnant women in South Asian population. These A1c changes were observed despite having significantly higher body max index among women in the T2 and T3 groups than in the T1 and non pregnant groups. To understand the factors determining the A1c decrease in pregnancy and to validate the findings of this study, we recommend further prospective studies among South Asian women
Keywords: Asian, Gestational diabetes, HbA1c , Pregnancy trimesters, Reference values.
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