Birth Weight and Maternal Glycated Haemoglobin in Pregnancies Complicated by Type 1 Diabetes

Abstract

Aim To re-examine the relationships between birth weight and maternal glycated haemoglobin (HbA1c) concentration at different time points in pregnancies complicated by pre-gestational type 1 diabetes. Methods A dataset was collected prospectively on all deliveries in Scotland to women with pre-gestational type 1 diabetes occurring during two 12 month periods (01/04/98 to 31/03/99 and 01/04/03 to 31/03/04). Relationships between standardised measures of birth weight and HbA1c at each time point were examined using correlation analysis. Results Standardised birth weights (Z scores) were calculated for 338 singleton live born infants. HbA1c concentrations were available for: 204 women (pre-pregnancy), 297 women (1st trimester), 314 women (2nd trimester) and 303 women (3rd trimester). Standardised birth weight showed a unimodal distribution shifted to the right relative to a reference population (Mean, +1.62 S.D). There was a significant negative correlation between pre-pregnancy HbA1c and birth weight (Spearman's Rho -0.138; p=0.049). Conclusions Standardised birth weights of the infants of diabetic mothers are higher than those of a reference population. There is no simple relationship between maternal glycaemic control and birth weight, but the previously described paradoxical inverse relationship between pre-pregnancy glycaemic control and birth weight has been confirmed using a larger dataset.