Tight or less tight glycaemic targets for women with gestational diabetes mellitus for reducing maternal and perinatal morbidity? (TARGET): study protocol for a stepped wedge randomised trial

Gestational diabetes mellitus (GDM) is strongly associated with significant adverse maternal and perinatal health outcomes that have lifelong consequences. Treatment for women with GDM aims to normalise maternal blood glucose concentrations to reduce these adverse health risks. Target recommendations for glycaemic control in women with GDM vary amongst international organisations. All their recommendations rely on consensus, as there have been no published randomised trials that compare different intensities of glucose control in women with GDM. The TARGET Trial aims to determine whether tighter targets for glycaemic control in women with GDM compared with less tight targets, reduce maternal and perinatal morbidity without adverse health consequences.

Using a stepped wedge, cluster randomised trial the 10 participating hospitals will be randomised to the timing of the change from the less tight to the tighter glycaemic target period. During the less tight target period, all health professionals at the hospital will aim to use the less tight glycaemic targets for treatment of women with GDM (fasting plasma glucose < 5.5 mmol/L; 1 h postprandial < 8.0 mmol/L; 2 h postprandial < 7.0 mmol/L). During the tighter target period all health professionals at the hospital will aim to use the tighter glycaemic targets for treatment of women with GDM (fasting plasma glucose ≤5.0 mmol/L, 1 h postprandial ≤7.4 mmol/L; 2 h postprandial ≤6.7 mmol/L). The primary study outcome is large for gestational age infant (birth weight > 90th centile). A sample size of 1080 participants will detect a treatment difference of 6% in the proportion of large for gestational age babies from 13% with less tight glycaemic targets to 7% with tighter targets, assuming an intra-cluster correlation coefficient of 0.05.

The TARGET Trial will provide high-level evidence of direct relevance for clinical practice. If tighter treatment targets for women with GDM clearly result in significantly fewer large for gestational age infants and less adverse maternal and perinatal outcomes then they should be recommended for women with GDM. This would be of great importance to these women, their children, health services and communities.

Australian New Zealand Clinical Trials Registry - ACTRN 12615000282583.