Aims: Follow 600 pregnant women in regional and remote Western Australia to delivery, to assess effectiveness of the OGTT in detecting adverse GDM-related perinatal outcomes.
Methods: Forty-one primary healthcare clinics across the Kimberley, Mid-West, Goldfields, Southwest and Great Southern regions participated between 1st January 2015 to 1st February 2018. Women, aged 16-years or over, at first antenatal presentation, were invited to participate. Women with confirmed diagnosis of diabetes mellitus or multiple pregnancy were excluded. Routine maternal and birth data were collected and GROW Customized Birth Weight Centiles calculated. OGTT [mmol/L] results were categorised based on the Hyperglycemia and Adverse Pregnancy Outcome (HAPO) Study (fasting: 2.5-4.1, 4.2-4.4, 4.5-4.7, 4.8-4.9, 5.0-5.2, 5.3-5.5, 5.6-5.8; 1-hour: 2.5-5.8, 5.9-7.3, 7.4-8.6, 8.7-9.5, 9.6-10.7, 10.8-11.7, ≥11.8; 2-hour: 2.5-5.0, 5.1-6.0, 6.1-6.9, 7.0-7.7, 7.8-8.7, 8.8-9.8, 9.9-11.1). GDM diagnosis was based on IADPSG criteria. Two study General Practitioner Obstetricians, blinded to routine investigations, independently determined if adverse perinatal outcomes were likely GDM-related.
Results: Of 694 recruited participants, 604 (66% with one or more high-risk factor) continued participation (39% Aboriginal) and delivered after 24 weeks gestation. Only 61% adhered to 2014 ADIPS screening recommendations. Sixty-seven (11%) met the criteria for GDM. Women screened at 24-32 weeks were significantly more likely to be in a lower glucose category compared with the HAPO cohort (fasting: OR 3.4; 95% CI 2.8-4.0, p<0.0005; 1-hour: OR 1.7, 95% CI 1.4-2.0, p <0.0005; 2-hour: OR 1.4, 95% CI 1.2-1.7, p <0.0005). Glucose instability in our cohort was a likely consequence of delays in laboratory testing (median time-to-analysis: 4.4 hours vs HAPO <1 hour). Preliminary analysis suggest 79% of mothers of infants with composite outcome of birth weight >90th centile and/or neonatal hypoglycaemia, had a normal OGTT or were not tested.
Conclusions: In this high-risk for GDM population, the OGTT was poorly accepted and not implemented according to strict pre-analytical guidelines. Consequently, this one-step screening and diagnostic tool fails to identify women who would likely benefit from intervention.