Randomised Controlled Trial of Gestational Treatment With Ursodeoxycholic Acid Compared to Metformin to Reduce Effects of Diabetes Mellitus

GUARD is a two-armed, randomised, controlled, open label multicentre clinical trial with optional observational mechanistic study in a subgroup from each arm, comparing Ursodeoxycholic Acid to Metformin (both oral BD). H0 is no difference in in maternal fasting glucose at 36 weeks. HA is a difference of 6% (0.28mmol/L), consistent with previously reported differences with UDCA treatment for non-alcoholic fatty liver disease (NAFLD). The RCT design was chosen as the generally accepted way of demonstrating clinically important effects of medical treatment, prior to their general acceptance into medical care. The open label is due to the practical difficulty of matching the treatments, due to pill sizes and different dosages.

At present it is known that not all women with GDM respond to oral metformin treatment. Some women cannot tolerate the drug and it is ineffective in others. Many women are reluctant to take insulin as this requires injections and is not without the risk of hypoglycaemia. Therefore there is a need for additional oral treatments to improve glycaemic control. UDCA is a reasonable drug to study as it has good safety data for use in pregnancy (due to studies in women with cholestasis in pregnancy). If previous trials of women with cholestasis is was shown to reduce insulin resistance. It also reduced umbilical cord lipid concentrations. Therefore it is reasonable to compare UDCA to metformin as it may have an equivalent (or better) impact upon glucose control and, if women with GDM have a similar response to those with cholestasis in pregnancy, it could be associated with better outcomes for the baby, e.g. improved umbilical cord blood lipids. As it has not been studied before The investigators do not know if it will be effective, but the existing data suggest it is reasonable to study UDCA. As there is the option of treatment with insulin for women that do not have acceptable glucose control when taking UDCA (as there is for metformin) both drugs are used with an acceptable alternative treatment if they are not sufficiently effective at achieving glycaemic control.

The investigators plan recruitment to last for 18-24 months, and a further 12 months to allow for close out activities.

According to sample size calculations, enrolling 158 participants will provide sufficient statistical power to detect the primary outcome, and allow for a 20% withdrawal rate. An additional 40 participants will be enrolled onto GUARD MEC to serve as controls for this part of the research. Participants will be identified following their OGTT appointment and approached by the diabetes nurse or the study midwife, ideally when they receive dietary and lifestyle education. Interdepartment co-operation will be required.

The Independent Data Monitoring Committee (IDMC) will review outcomes after 25% of the participants have given birth. Data will be monitored by the IDMC at intervals to ensure the interest of participants and validity of data is safeguarded. Most of the outcomes are clinical samples, objective measurements and patient questionnaires. As such researcher bias should have a minimal impact on the reporting. Should this be identified, it will be escalated to the Trial Steering Committee for decision.