RCT Metformin for Reduction of Gestational Diabetes Mellitus Effects

Inclusion criteria

• Willing and able to provide written informed consent
• Participants aged 18-50
• Pregnancy gestation up to 28 weeks (+ 6 days) confirmed by positive pregnancy test
• Singleton pregnancy as determined by scan
• Positive diagnosis of Gestational Diabetes Mellitus on a Oral Glucose Tolerance Test (OGTT) according to the International Association of the Diabetes and Pregnancy Study Groups (IADPSG) criteria if any one of the following are achieved: i) Fasting glucose >/= 5.1mmol/l and <7mmol/l, or ii) 1 hour post glucose load of >/=10mmol/l, or iii) 2 hour post glucose load of >/=8.5 mmol/l and <11.1mmo/l
• Resident in the locality and intending to deliver within the trial site

Exclusion criteria

• Participants who have an established diagnosis of diabetes (Type 1, Type 2, Monogenic or secondary)
• Participants with a fasting glucose > 7mmol/l or a 2h value > 11.1 mmol/l
• Multiple pregnancies (twins, triplets etc.) as determined by scan
• Known intolerance to metformin
• Known contraindication to the use of metformin which include: i) renal insufficiency (defined as serum creatinine of greater than 130 µmol/L or creatinine clearance <60 ml/min), ii) moderate to severe liver dysfunction (aspartate aminotransferase (AST) and alanine aminotransferase (ALT) greater than 3 times the upper limit of normal, iii) shock or sepsis, and iv) previous hypersensitivity to metformin
• Major congenital malformations or an abnormally deemed unsuitable for metformin by the site PI or attending consultant
• Known small for gestational age (Small for gestational age (SGA) refers to foetal growth less than the 10th percentile (RCOG, 2014), or if foetal growth is deemed unsatisfactory by the treating obstetrician)
• Known gestational hypertension or pre-eclampsia or ruptured membranes
• Participants who have a history of drug or alcohol use that, in the opinion of the investigator, would interfere with adherence to study requirements
• Participants with significant gastrointestinal problems such as severe vomiting, Crohn's disease or colitis which will inadvertently affect absorption of the study drug
• Participants with congestive heart failure or history of congestive heart failure
• Participants with serious mental illness which would affect adherence to study medication or compliance with study protocol in the opinion of the investigator
• Patients with rare hereditary problems of galactose intolerance, the Lapp lactase deficiency or glucose-galactose malabsorption