title: Trimester-specific reference intervals for haemoglobin A1c (HbA1c) in pregnancy.
abstract: BACKGROUND
  Diabetes in pregnancy imposes additional risks to both mother and infant. These increased risks are considered to be primarily related to glycaemic control which is monitored by means of glycated haemoglobin (HbA(1c)). The correlation of HbA(1c) with clinical outcomes emphasises the need to measure HbA(1c) accurately, precisely and for correct interpretation, comparison to appropriately defined reference intervals. Since July 2010, the HbA(1c) assay in Irish laboratories is fully metrologically traceable to the IFCC standard. The objective was to establish trimester-specific reference intervals in pregnancy for IFCC standardised HbA(1c) in non-diabetic Caucasian women.
  
  
  METHODS
  The authors recruited 311 non-diabetic Caucasian pregnant (n=246) and non-pregnant women (n=65). A selective screening based on risk factors for gestational diabetes was employed. All subjects had a random plasma glucose <7.7 mmol/L and normal haemoglobin level. Pregnancy trimester was defined as trimester 1 (T1, n=40) up to 12 weeks +6 days, trimester 2 (T2, n=106) 13-27 weeks +6 days, trimester 3 (T3, n=100) >28 weeks to term.
  
  
  RESULTS
  The normal HbA(1c) reference interval for Caucasian non-pregnant women was 29-37 mmol/mol (Diabetes Control and Complications Trial; DCCT: 4.8%-5.5%), T1: 24-36 mmol/mol (DCCT: 4.3%-5.4%), T2: 25-35 mmol/mol (DCCT: 4.4%-5.4%) and T3: 28-39 mmol/mol (DCCT: 4.7%-5.7%). HbA(1c) was significantly decreased in trimesters 1 and 2 compared to non-pregnant women.
  
  
  CONCLUSIONS
  HbA(1c) trimester-specific reference intervals are required to better inform the management of pregnancies complicated by diabetes.
authors: Department of Medicine, College of Medicine Nursing and Health Sciences, National University of Ireland, Galway, Ireland.
authors: Catherine
authors: C
authors: O'Connor
authors: Paula Mary
authors: PM
authors: O'Shea
authors: Lisa Ann
authors: LA
authors: Owens
authors: Louise
authors: L
authors: Carmody
authors: Gloria
authors: G
authors: Avalos
authors: Laura
authors: L
authors: Nestor
authors: Katherine
authors: K
authors: Lydon
authors: Fidelma
authors: F
authors: Dunne
mesh_terms: D000293:Adolescent; D000328:Adult; D001774:Blood Chemical Analysis / Q000592:standards*; D005260:Female; D006442:Glycated Hemoglobin / Q000032:analysis*; D006801:Humans; D008875:Middle Aged; D011247:Pregnancy; D011264:Pregnancy Trimesters / Q000097:blood*; D012016:Reference Values; D044465:White People / Q000706:statistics & numerical data; D055815:Young Adult
chemical_list: D006442:Glycated Hemoglobin; C517652:hemoglobin A1c protein, human