The proposed IADPSG criteria for diagnosis and management of GDM1 will impact both on women so diagnosed and on healthcare resources invested in such management. The new criteria, based on the HAPO study2 , have not been subjected to RCT to establish their superiority over existing criteria with regard to clinical benefit to mothers or offspring either short or longer term, or to assess their cost-effectiveness and economic sustainability.
We plan two concurrent RCTs to investigate these proposals within the SA population, together with a nested population study to assess the prevalence of the 12 most common MODY gene variants in women diagnosed with GDM, and a careful health economic analysis of the costs/benefits of the interventions over the first two years of the lives of the offspring.
Trial A: women not previously diagnosed diabetic will be tested with a 2h 75g OGTT at 24-28 weeks gestation, or earlier if at increased GDM risk. Those with fasting glucose 5.1-5.4 mmol/L will be randomised to observation ("not GDM") or treatment ("mild GDM"). Women with 2h glucose ≥8.0 mmol/L will be treated as GDM.
Trial B: women diagnosed with ADIPS GDM will be randomised to “very tight control”: target fBGL <5.0 mmol/L, 2hppBGL <6.7 mmol/L, or “tight control”: target fBGL <5.5 mmol/L, 2hppBGL <7.0 mmol/L.
Primary outcomes: LGA, pre-eclampsia.
1350 women will be sufficient to show with active management of "mild GDM" a 40% reduction in the risk of LGA (alpha 0.05 two-tailed, 90% power, 4% loss to follow up) from 15% to 9%, and a 49% reduction in the risk of pre-eclampsia from 10% to 5.1%. 718 women will be sufficient to exclude a difference in the risk of LGA with "very tight control" of GDM of more than 8% (alpha 0.05 two-tailed, 90% power, 4% loss to follow up).
We anticipate a 3.5 year recruitment and 18-24 month follow-up.