Maternal glycated haemoglobin, pre-gestational weight, pregnancy weight gain and risk of large-for-gestational-age babies: a Danish cohort study of 209 singleton Type 1 diabetic pregnacies

Aims To examine the association between maternal glycated haemoglobin in the second half of diabetic pregnancies and the relative risk of delivering large-for-gestational-age (LGA) babies, controlling for maternal body mass index (BMI) before pregnancy, weight gain, age, White class and smoking habits.

Methods We identified all pregnant diabetic women in North Jutland County, Denmark from 1985 to 2003. Data on HbA_1c values from the 20th gestational week to term were collected from medical records and the babies were classified as large, normal or small for gestational age. The association between glycated haemoglobin (HbA_1c) and relative risk of delivering an LGA baby was quantified based on logistic regression models and stratified analysis controlling for the five covariates.

Results We included 209 singleton pregnancies with assessable HbA_1c values of which 59% [95% confidence interval (CI) 52-65%] terminated with an LGA baby. Increasing levels of HbA_1c, BMI and weight gain were all associated with increasing risk of delivering an LGA baby. Analyses stratified according to maternal BMI showed that the association between HbA_1c and risk of delivering an LGA baby was restricted to pregnancies with pre-pregnancy BMI > 23 kg/m². We found no association between HbA_1c and risk of delivering an LGA baby in pregnancies with lower BMI.

Conclusion The positive association between glycated haemoglobin and birth of an LGA baby seems to be restricted to women with BMI > 23 kg/m².