Background Diabetes and obesity are major public health problems in Tonga, predicting a substantial risk from hyperglycaemia in pregnancy (HIP) including gestational diabetes (GDM) and diabetes in pregnacy (DIP). Tonga provides free antenatal care which is attended by 98% of women. The Ministry of Health introduced systematic sceening for GDM in 2016 across the main island of Tongatapu. We now describe the prevalence of GDM and DIP and associated GDM risk factors.
Methods Women who attended the antenatal services on Tongatapu between 1/1-31/12 2016 attended for a 75g oral glucose tolerance test (OGTT) at 24 weeks. Women with eg past GDM were refrred for an early OGTT. DIP and GDM were diagnosed if fasting glucose (FBG) was ≥7.0 or 5.3-6.9 mmol/l respectively or 2 hour postprandial glucose was ≥11.1 or 9.0-11.0 mmol/l respectively. OGTTs were undertaken at Vaiola Hospital using one laboratory. Clinical data prospectively collected included age, GDM risk factors and body mass index (BMI: obesity cut off ≥32.0 kg/m2).
Results Overall, 1638 women attended, of whom 1625 (99.2%) completed the OGTT; mean age was 28±6 years and mean BMI 34.6±7.2; 63.7% were obese. 8.4% had GDM and 2.1% DIP. The prevalence of GDM/DIP increased significantly (p<0.001) with age (<25 years, 25-29.9 years, 30-34.9 years, 35+ years: 3.4%, 5.9%, 13.5%, 13.6%/0.8%, 0.7%, 3.3%, 4.6% respectively). The prevalence of GDM/DIP increased significantly with BMI (3.4%, 5.7%, 9.7%, 13.4%/0.7%, 1.5%, 2.6%, 1.9%, p<0.001), past GDM (21.9% vs 10.%, p<0.05) and family history of diabetes (16.5% vs 7.3%, p<0.001). After adjustments, the prevalence of HIP increased significantly with family history (OR 2.37; 95%CI:1.64-3.42) and age [1.48(0.78-2.81), 3.69(2.05-6.63), 4.97(2.72-9.08), respectively] but not BMI or past GDM. Isolated high FBG, 2HBG and both FBG/2HBG were present in 6.8%, 0.7% and 2.9% women respectively.
Conclusion. A high proportion of Tongan women with HIP have DIP and particularly fasting hyperglycemia. Age appears to be a more important risk factor than obesity in this population.