The rising tide of global obesity and diabetes has seen Gestational Diabetes Mellitus (GDM) assume increasing public health significance. More than a third of pregnant women in the developed world present for care with a body mass index consistent with overweight or obesity [1-3]. Many pregnant women also have gestational weight gain in excess of Institute of Medicine recommendations [1-4]. These changes have seen global rates of GDM soar.

Until recently, the diagnosis and management of GDM was based upon expert opinion. Following publication of the hypoglycaemiaand Adverse Pregnancy Outcomes (HAPO) trial in 2008, it became possible to conduct trials and evaluate clinical service against outcomes that could be directly linked to pregnancy hyperglycaemia [5].

The HAPO trial of 23,316 women documented clear associations between hyperglycaemia at 24-28 weeks gestation and adverse maternal and neonatal outcomes [5]. Results revealed a continuum across which glycaemia levels were associated with adverse outcomes. In the absence of a categorical cut off, the International Association of Diabetes and Pregnancy Study Groups (IADPSG) panel recommended the diagnostic criteria should be blood sugar levels that were associated with an odds ratio of 1.75 for producing adverse outcomes compared to mean glucose levels [6].

Whilst no trial has specifically utilised these cut off points, randomised trials of intervention in women with mild hyperglycaemia in pregnancy have documented a broad range of benefits including reductions in birth weight >90^th centile, caesarean section, neonatal hypoglycaemia and cord C-peptide >90^th centile [7-9].

Following an evaluation of data from available trials, authorities recommended new criteria to diagnose GDM (Table 1). These targets are based upon blood sugar levels following a 75 g Oral Glucose Tolerance Test (OGTT) performed between 24-28 weeks gestation. Treatment targets have also been refined in line with results from these published trials and expert opinion (Table 2)[7-11].

Table 1: Diagnosis of Gestational Diabetes Mellitus

Table 2: Treatment targets for Gestational Diabetes Mellitus

Unfortunately, achieving consensus in the diagnosis and treatment targets for GDM is only the starting point. Clinicians now face the challenge to deliver care for women whose pregnancy is complicated with GDM so that therapeutic outcomes are achieved in a cost effective way.

Since the aim of care is to achieve glycaemic control, dietary interventions are key. However, dietary interventions range in price. The cheapest models provide women with a written pamphlet. The next step up would be models of care where a patient educator provides patients with written information and dietary counselling, through to group sessions with a qualified dietician, to repeated individualised sessions with a dietician at the extreme price range. The cost of these interventions ranges from US$1 to US$300 per patient [2]. A direct comparison of the relative efficacy of these differing approaches, with other factors controlled, has not occurred.

The next question is drug therapy. Fortunately, nearly 70% of patients with GDM can be managed with dietary intervention alone. However, the remaining patients require medication. Until recently this was exclusively administered as insulin, but in recent years Metformin has been substituted for insulin with comparable outcomes [12,13]. However, patients with high blood sugar levels usually benefit from insulin or combined therapy [13].

The type of monitoring required in pregnancy complicated by GDM is also unclear. Fetal cardiotocography and ultrasound have been utilised to manage pregnancy but their ‘value add’ in management is unclear [7-9].

Likewise, the ideal time to deliver patients whose pregnancy is complicated by GDM is subjected to debate. When fetal compromise is present, timing of delivery is dependent upon fetal factors. However, it is less clear whether a pregnancy complicated by GDM but subsequently managed with good glycaemic control and normal fetal growth should warrant induction or be left to await natural labour.

Postnatal management is also diverse. Some centers monitor babies for 48 hours with serial blood sugar levels whilst others are happy for expedited discharge.

Strangely the one intervention that has a substantiated evidence base, a postnatal OGTT performed between 6-12 weeks postpartum to detect women with type 2 diabetes, seems to slip through the practice net. Studies show up to 16% and 6% of women with GDM will have ongoing glucose intolerance or type 2 diabetes respectively by three months postpartum. Therefore, this patient population represents a cohort where early diagnosis and intervention could achieve benefits in terms of long term chronic disease morbidity [14]. Yet follow up is inconsistent [15].

Clinicians need to streamline the management of GDM to ensure interventions are effective and efficient. Streamlined pathways are required to deliver dietary advice, monitor glycaemia and monitor fetal wellbeing without undue intervention secondary to antenatal tests and labour induction.

These are the next wave of challenges for clinicians.