Gestational diabetes mellitus screening, management and outcomes in the Cook Islands

Abstract

The Cook Islands consists of 15 islands and atolls with a resident population of about 15,000 at the 2011 Census, of whom 88% were Cook Island Māori and the remainder mostly New Zealand European.1 There are 3655 female residents in the reproductive age group (15 to 49 years).1 Obesity and diabetes represent a significant health challenge: 66% of adult women are obese and 21% have diabetes.2 These rates are similar to other Pacific countries.3,4 There is no universally agreed approach to screening for gestational diabetes (GDM) or even agreement on appropriate glucose thresholds at which gestational diabetes is diagnosed.5–7 Screening programmes inevitably need to balance the performance of different approaches to screening with the resources available.7–9 Universal screening for gestational diabetes has been offered to all eligible women in Rarotonga, the Southern Group Islands and some of the Northern Group Islands since January 2009. The diagnosis of GDM in the Cook Islands has been made using a two-step approach late in the second trimester. An initial screening test involves a non-fasting 50 gram (g) glucose challenge test (GCT) at 24–28 weeks gestation. Women are subsequently offered a diagnostic 75 g oral glucose tolerance test (OGTT) if their 1-hour glucose concentration is ≥7.8 mmol/L.10,11 GDM is diagnosed if the fasting sugar glucose (FBG) is ≥5.2 mmol/L and/ or the 2-hour glucose concentration is ≥8.0 mmol/L,7,11 (compared to the New Zealand criteria of FBG ≥5.5, 2H ≥9.0 mmol/L). Pregnancy impaired glucose tolerance (pIGT) is diagnosed if the GCT is positive but the GDM test is negative. Alternative screening strategies could include universal first trimester testing or enhanced first and second trimester screening for women at increased risk of gestational diabetes. Such approaches have been suggested by the International Association of Diabetes in Pregnancy Study Groups (IADPSG),7,11 the American Diabetes Association (ADA)12 and the National Institute for Clinical Excellence (NICE) in the UK.13 The New Zealand Ministry of Health is also developing plans for a new screening programme for gestational diabetes. The aim of this study is to determine how many women are being diagnosed with GDM using the current screening criteria and to compare pregnancy outcomes in women with and without GDM using the current criteria.