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Trimester-specific reference intervals for haemoglobin A1c (HbA1c) in pregnancy
Catherine O'Connor1, Paula Mary O'Shea, Lisa Ann Owens
1Department of Medicine, College of Medicine Nursing and Health Sciences, National University of Ireland, Galway, Ireland.
Establishing trimester-specific reference intervals for glycated haemoglobin (HbA1c) in pregnant women is crucial for accurate diabetes management. These intervals differ significantly from non-pregnant women, especially in early pregnancy.
Area of Science:
- Clinical Chemistry
- Endocrinology
- Maternal-Fetal Medicine
Background:
- Diabetes in pregnancy presents risks to mother and infant, primarily linked to glycemic control monitored by HbA1c.
- Accurate HbA1c measurement and interpretation require appropriate reference intervals.
- Irish laboratories use IFCC-standardized HbA1c assays traceable since 2010.
Purpose of the Study:
- To establish trimester-specific reference intervals for IFCC-standardized HbA1c.
- To define these intervals in non-diabetic Caucasian pregnant women.
- To compare HbA1c levels across pregnancy trimesters and with non-pregnant individuals.
Main Methods:
- Recruited 311 non-diabetic Caucasian women (246 pregnant, 65 non-pregnant).
- Employed selective screening for gestational diabetes risk factors.
- Defined pregnancy trimesters: T1 (up to 12w6d), T2 (13-27w6d), T3 (>28w to term).
Main Results:
- Established HbA1c reference intervals: Non-pregnant: 29-37 mmol/mol; T1: 24-36 mmol/mol; T2: 25-35 mmol/mol; T3: 28-39 mmol/mol.
- HbA1c levels were significantly lower in T1 and T2 compared to non-pregnant women.
- Provided corresponding Diabetes Control and Complications Trial (DCCT) values for each interval.
Conclusions:
- Trimester-specific HbA1c reference intervals are essential for improved pregnancy management in diabetic cases.
- Current non-pregnant reference intervals may not be suitable for pregnant populations.
- Accurate glycemic monitoring through tailored HbA1c intervals aids better clinical decision-making.
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