Oral Presentation Australian Diabetes Society and the Australian Diabetes Educators Association Annual Scientific Meeting 2017

Glycaemic variability is associated with accelerated foetal growth and large for gestational age neonates in women with type 1 diabetes (#182)

Rachel T McGrath 1 2 3 , Sarah J Glastras 1 2 3 , Sean K Seeho 4 , Emma S Scott 1 , Gregory R Fulcher 1 3 , Samantha L Hocking 1 3 5
  1. Department of Endocrinology, Royal North Shore Hosptital, St Leonards, NSW, Australia
  2. Kolling Institute, St Leonards, NSW, Australia
  3. Northern Clinical School, University of Sydney, Sydney, NSW, Australia
  4. Clinical and Population Perinatal Health Research, Kolling Institute, St Leonards, NSW, Australia
  5. Boden Initiative, Charles Perkins Centre, University of Sydney, Sydney, NSW, Australia

Introduction: Foetal exposure to hyperglycaemia is a major determinant of large for gestational age (LGA) (birth weight >90th centile for gender) neonates, yet targets for glycaemic control beyond the first trimester in type 1 diabetes (T1D) pregnancy remain controversial.

Objective: To determine the association between HbA1c or glycaemic variability (GV) (using J-index) and excess fetal growth in T1D pregnancy.

Methods: Continuous glucose monitoring (CGM) was performed and HbA1c measured in 21 women at 14-18 (t1), 24-28 (t2) and 32-36 (t3) weeks’ gestation. Abdominal circumference was estimated by ultrasound at 30 weeks’ gestation (AC30). The associations between HbA1c or J-index and AC30 and LGA were determined.

Results: 13 neonates had AC30 >90th centile. Of these, 8 neonates were born LGA. J-index at t2 was significantly more correlated with AC30 >90th centile than HbA1c at t2 (r=0.598, p=0.005 and r=0.444, p=0.043, respectively). The LGA group had significantly greater J-index than the non-LGA group at t2 and higher HbA1c at each time point (Figure 1A&B). Using univariate linear modelling, J-index at t2 maintained a significant independent association with birth weight centile (r2=0.229; p<0.05), whereas HbA1c did not (r2=0.008; p=0.713). Combining J-index and HbA1c at t2 resulted in a stronger association with birth weight centile (r2=0.477; p<0.01) than either measure alone, with mean values of 31.7 and 5.95%, respectively. Furthermore, ROC curve analysis demonstrated that using a cut-off of HbA1c >6% and J-index >30 at t2 identified all neonates that were born LGA (Figure 1C).

Conclusions: Elevated GV at 24-28 weeks’ gestation is more strongly associated with accelerated foetal growth at 30 weeks’ gestation and LGA neonates than HbA1c. Minimising GV in the second trimester may reduce the risk of foetal overgrowth in T1D pregnancy.

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Figure 1: Difference in A) J-Index and B) HbA1c for LGA vs. non-LGA neonates. C) ROC curve analysis.