Metformin in the Prevention of Gestational Diabetes: The MPG Trial

The study wishes to explore whether using metformin from early in the second trimester of pregnancy can reduce the risk of recurrence of gestational diabetes. The primary hypothesis is that "oral metformin, administered from early in the second trimester to women with a past history of gestational diabetes, will reduce the risk of recurrent gestational diabetes". Pregnant women who have had gestational diabetes in a previous pregnancy will be invited to participate. They must be between 12 and 16 weeks gestation at the time of study enrolment. Once a woman has given her informed consent she will undergo an oral Glucose Tolerance Test (oGTT) and a fasting blood sample will be stored for measurement of insulin and other hormones. Any women with a positive oGTT will not be eligible for the study and will be given appropriate counselling and treatment for her recurrent gestational diabetes (rGDM). Those who have a normal oGTT result will be eligible to have medication randomly allocated. Baseline demographic and clinical data will be collected. Women will be randomised to medication. Neither the woman nor the study team will know whether the woman is receiving active treatment or placebo. The woman will take her medication at the rate of one tablet per night for the next week. The dose will be increased by one tablet per week until a dose of four tablets a day is reached, or fewer as tolerated. Standard antenatal care will be received by all women on the study. At 26-28 weeks gestation participants will be weighed, measured and have repeat oGTT and blood sample as above. Any women found to have rGDM will continue with her study medication and receive appropriate counselling and treatment of the rGDM. At 35-36 weeks gestation the participants will again have a fasting blood sample taken, be weighed and measured. Birth of the baby will be planned in conjunction with obstetric team, depending on obstetric and medical factors present at the time. Study medication may be stopped at onset of labour or 12hours prior to a booked caesarean section. A sample of the cord blood will be collected for measurement of glucose, insulin and other hormones. The baby will receive standard care as for the baby of a diabetic mother. The baby will have standard measures done, along with some extra ones for the study. At 6 weeks after birth, the mother and baby will be measured again. The mother will undergo a repeat oGTT, as is standard for women with GDM, to determine if there is any ongoing diabetes or glucose intolerance. At this time a blood sample will again be taken for measurement of insulin and other hormones.