The relationship between birth weight and maternal glycated haemoglobin (HbA1c) concentration in pregnancies complicated by Type 1 diabetes.
OBJECTIVE
To examine the relationships between maternal HbA1c concentration at different time points and birth weight in pregnancies complicated by pre-existing Type 1 diabetes.


METHODS
A comprehensive audit dataset was collected prospectively on all deliveries in Scotland to women with pre-existing Type 1 diabetes occurring between 1 April 1998 and 31 March 1999. Data items included HbA1c concentrations prior to conception and in each of the three trimesters of pregnancy, and birth weight. Relationships between standardized birth weight and HbA1c concentrations at each of the four time points were examined using correlation analysis.


RESULTS
Standardized birth weight (Z scores) could be calculated for 203 of 208 singleton liveborn infants. HbA1c concentrations, standardized to correct for assay differences among hospitals, at different time points were available for between 134 (pre-pregnancy) and 192 (third trimester) cases. Standardized birth weight, relative to a reference population, showed a unimodal distribution, shifted to the right (mean, +1.57 sd). There was a significant negative correlation between pre-pregnancy HbA1c and birth weight (Spearman's R, -0.208; P = 0.016). There were no statistically significant correlations for other time points.


CONCLUSIONS
Standardized birth weight scores of the infants of diabetic mothers are higher than those of a reference population. There is no simple relationship between maternal glycaemic status and birth weight, but there appears to be a paradoxical inverse relationship between pre-pregnancy glycaemic control and standardized birth weight.
Penney
G C
GC
University of Edinburgh, UK. g.c.penney@abdn.ac.uk
Mair
G
G
Pearson
D W M
DW
D001724:Birth Weight; D015331:Cohort Studies; D003922:Diabetes Mellitus, Type 1 / Q000097:blood*; D005260:Female; D006442:Glycated Hemoglobin / Q000032:analysis*; D006801:Humans; D007223:Infant; D011247:Pregnancy; D011254:Pregnancy in Diabetics / Q000097:blood*; D011446:Prospective Studies
D006442:Glycated Hemoglobin