Poster Presentation International Association of the Diabetes and Pregnancy Study Groups 2022 - Hosted by ADIPS

Prediabetes and pregnancy: A lower first trimester HbA1c threshold of 5.6% identifies preconception prediabetes and high risk for adverse perinatal outcome (#114)

Julia Marley 1 , Erica Spry 1 2 , Emma Jamieson 3
  1. The Rural Clinical School of Western Australia, The University of Western Australia, Broome, WA, Australia
  2. Kimberley Aboriginal Medical Services, Broome, WA, Australia
  3. The Rural Clinical School of Western Australia, The University of Western Australia, Bunbury, WA, Australia

Background

ADIPS recommend that women with preconception prediabetes are managed as having GDM from the start of their pregnancy. However, clinical implementation is problematic: prediabetes screening in high-risk women of reproductive age is low, there is considerable variation in guidelines for early screening for hyperglycaemia in pregnancy (HIP), and thresholds fail to account for the drop in glucose and HbA1c levels in first trimester. A lower first trimester HbA1c threshold may improve detection of preconception prediabetes.

Methods

Twenty-seven rural and remote clinics in Western Australia recruited 694 pregnant women (39% Aboriginal women) from 2015-2018. Another 951 pregnant women (96.2% Aboriginal women) attending a Kimberley Aboriginal Community Controlled Health Service (ACCHS) in 2018-2021 were included in a retrospective audit. HbA1c was measured with first antenatal investigations (<20-weeks gestation). OGTT collection and measurement was conducted following local pathology guidelines; to prevent glycolysis Kimberley ACCHS adopted fluoride/citrate/EDTA (FC) tubes in September 2019. Large-for-gestational-age (LGA) newborn was defined as birthweight greater than 90th centile (calculated using Perinatal Institute GROW v8.0.1). Outcome measures included: area under the curve (AUC), receiver operator characteristics (ROC) curve derived high-risk (specificity ≥90%) cut-point for HbA1c for abnormal corrected-OGTT; RR [95% CI] for LGA newborn.

Results

Five-hundred and ninety women (397 prospective, 193 retrospective) had an HbA1c <20-weeks and OGTT after 24-weeks gestation. Stratifying ROC curves by Aboriginal status improved the AUC of early HbA1c for an abnormal routine OGTT for women at high risk of preconception prediabetes (all women: 0.63; Aboriginal women: 0.70; non-Aboriginal women: 0.57). An early HbA1c ≥5.6% was the optimal cut-point to identify women with an abnormal OGTT. Women above this threshold had 2.16 [1.33-3.51, P =0.002] relative risk for LGA newborn compared to women below the threshold and with a normal routine OGTT. Using a first trimester HbA1c ≥5.6% as the threshold for preconception prediabetes we estimate 16% of Aboriginal women will need appropriate management from early in pregnancy. Another 12% of Aboriginal women will develop GDM later in pregnancy.

Conclusions

Lowering the first trimester HbA1c threshold to 5.6% should simplify early pregnancy screening for preconception prediabetes in high-risk populations and identify more than half of the women who would later have an abnormal OGTT. Women who are normoglycaemia in first trimester will need to complete an OGTT ≥24-weeks gestation to identify development of GDM.