Poster Presentation Australasian Diabetes in Pregnancy Society Annual Scientific Meeting 2024

Can Using a Fasting Glucose Threshold of 4.7mmol/L Replace the Oral Glucose Tolerance Test for the Diagnosis of Gestational Diabetes? (#23)

Han HS Shi 1 2 , Liam LC Clifford 1 2 , Jeff JF Flack 1 2 3 , Sarah SA Abdo 1 2 , Quynh QL Le 1 , Stephanie ST Terry 1 , Natasha ND Diwakar 1 , Wenjie WW Wang 1 , Cunjing CL Li 1 , Jenny JW Wright 1 , Tang TW Wong 1 2 3
  1. Diabetes Centre, Bankstown-Lidcombe Hospital, Sydney, NSW, Australia
  2. Faculty of Medicine and Health, University of New South Wales, Sydney, NSW, Australia
  3. Department of Medicine, Western Sydney University, Sydney, Sydney, NSW, Australia

Background:

It has been proposed that using a fasting glucose threshold of 4.7mmol/L could be utilised to triage the need for a 75g OGTT with respect to GDM screening1.

Aim:

  • To assess the distribution of fasting glucose in women diagnosed with GDM.
  • To determine if there are differences in maternal characteristics and pregnancy outcomes in patients with fasting glucose levels below and above 4.7mmol/L.

Methods:

We examined de-identified prospectively collected demographic and outcome data from singleton GDM pregnancies (March 2016 to March 2024), diagnosed according to ADIPS2014 criteria. All women received education on glucose monitoring and medical nutritional therapy. Insulin was commenced if treatment targets were not met (FBGL < 5.3mmol/L, 1hrBGL < 7.4, 2hrBGL < 7.0). Metformin was not used. Two groups were defined: low fasting (LF) and higher fasting (HF) glucose groups, based on whether women had fasting glucose levels below or equal to/above 4.7mM, respectively. We compared differences in demographic and outcome findings between the groups. Outcomes assessed included insulin use, caesarean section, early delivery (<37 weeks), LGA (>90th percentile), SGA (<10th percentile), neonatal hypoglycaemia (<2.6mmol/L), and neonatal jaundice (requiring phototherapy).

 

Results:

There were 3127 singleton GDM pregnancies in our multi-ethnic population. Mean fasting glucose was 5.1±0.7mmol/L and were “normally distributed”. 32.7% (1023/3127) of women with GDM have fasting glucose levels <4.7mmol/L. Compared to the HF group, the LF counterpart had lower gravida (2.7±1.8vs3.0±1.9), parity (1.2±1.2 vs 1.4±1.4), BMI (24.9±4.9 vs 28.1±6.3kg/m2), total gestational weight gain (11.3±5.6 vs 12.1±7.0kg), and 1hr-OGTT (9.6±2.2 vs 10.2±1.3mmol/L) and 2hr-OGTT parameters (7.6±1.9 vs 8.3±1.6mmol/L). There was a higher proportion of East and South-Asian women in the LF group (35.2% vs 17.3%, p<0.0001) compared to HF group, all p<0.0001. Notably, the largest ethnicity in the LF group was also East/Southeast Asian women. There were lower rates of  caesarean section (31.9% vs 37.6%, p<0.01) and LGA (9.8% vs 13.6%, p<0.01). Notably, LF women had lower but still significant rates of insulin use (30.2%, vs 56.2%, p<0.0001) and a higher rate of “bolus only” insulin therapy (12.4 vs 4.9%, p<0.0001).

 

Conclusion:

Contrary to recent findings, our study suggests that employing a fasting threshold of <4.7mmol/L would overlook a significant number of women with GDM, particularly those of East and Southeast Asian ethnicity. Although rates of caesarean section and LGA were lower in LF women, this may have been mediated by the very significant rates of insulin use (30%) in these women.

 

 

GWG: Gestational Weight Gain, OGTT: Oral Glucose Tolerance Test, LGA: Large for Gestational Age, SGA: Small for Gestational Age