Oral Presentation Society of Obstetric Medicine of Australia and New Zealand and Australasian Diabetes in Pregnancy Society Joint Scientific Meeting 2017

Excess Foetal Growth and Glycaemic Control in Type 1 Diabetes and Pregnancy (#13)

Stefanie Ring 1 2 , Sarah J Glastras 1 2 3 , Samantha L Hocking 1 2 , Sean K Seeho 4 , Gregory R Fulcher 1 2 , Rachel T McGrath 1 2 3
  1. Endocrinology, Royal North Shore Hospital, St Leonards, NSW, Australia
  2. Northern Clinical School, University of Sydney, Sydney, NSW, Australia
  3. Kolling Institute of Medical Research, Sydney, NSW, Australia
  4. Clinical and Population Perinatal Health Research, Kolling Institute, St Leonards, NSW, Australia

Introduction: A common complication of type 1 diabetes (T1D) is large-for-gestational-age (LGA) neonates (birthweight >90th centile for gender); however, the contribution of hyperglycaemia throughout pregnancy towards excess foetal growth is unclear.

Objectives: To examine the relationship between glycaemic control in each trimester of pregnancy and the incidence of excess foetal growth and LGA neonates in women with T1D.

Methods: In this retrospective, cohort study, 70 pregnancies in 61 women attending Royal North Shore Hospital, Sydney during 2012-2017 were identified. The Intergrowth-21st Project birthweight and Hadlock foetal abdominal circumference (AC) centiles were used to identify LGA neonates and excess foetal growth, respectively.

Results: The mean ± SD maternal age was 32.5 ± 5.4 years, with T1D duration of 15.4 ± 9.1 years and first trimester BMI of 26 ± 5kg/m2. Thirty-nine neonates (56%) were LGA with a mean birth weight of 3,483 g, with 18 (46%) being macrosomic (birthweight >4000 g). Mothers of LGA neonates had significantly higher HbA1c levels in the first (p < 0.0001), second (p < 0.0001) and third (p = 0.002) trimesters and prior to conception (p = 0.004). Neonates born LGA had significantly greater AC by 28 weeks’ gestation compared to non-LGA neonates (p = 0.0014), which was positively associated with second trimester HbA1c (r = 0.365; p = 0.021). Likewise, foetal AC at 34 weeks correlated with third trimester HbA1c (r = 0.404; p = 0.008). Using an HbA1c cut-off of 6% showed that second trimester HbA1c was more predictive of LGA neonates than third trimester HbA1c (sensitivity 74.1%, specificity 83.3% vs. sensitivity 69.2%, specificity 61.9%, respectively). There was no significant difference in early maternal BMI, maternal age or T1D duration between groups.

Conclusions: Achieving tight glycaemic control with an HbA1c below 6% by the second trimester may prevent excess foetal growth in T1D pregnancy.