Gestational diabetes mellitus (GDM) is one of the most common medical complications of pregnancy and has serious health implications for both the pregnant woman and her child. In particular, offspring of mothers with GDM have an increased prevalence of obesity, diabetes and metabolic syndrome, perpetuating serious health consequences in subsequent generations.

Although regular exercise offers numerous benefits for both the mother and her child, its effectiveness in preventing GDM remains to be established. It has been recently shown that regular supervised home-based exercise may attenuate the decline in glucose tolerance in obese pregnant women. This study aims to conduct a single-centred, multi-sited, single-blinded randomised controlled trial examining the effect of 14 weeks of supervised home-based exercise (commenced at 14 weeks gestation) on the recurrence and severity of GDM, along with other aspects of maternal and fetal wellbeing.

Eligible participants (n = 200) will be randomly allocated to an exercise intervention (n = 100) or a control group (n = 100). The exercise intervention will involve three 60-minute home-based, supervised exercise sessions each week. This type of program overcomes many of the barriers to exercise in this population including transportation, child care issues and embarrassment associated with exercising in a public venue. The investigators have already shown this program to be both feasible and warmly accepted by obese pregnant women.

Inclusion Criteria:

• women at 12-13 weeks gestation, with a history of gestational diabetes in a previous pregnancy.

Exclusion Criteria:

• unable to participate in the supervised 14 week home-based exercise program
• less than 18 years of age
• unable to understand the implications of participation in the trial
• women with a multiple pregnancy
• women with pre-existing diabetes (type 1 or 2) or cardiac disease
• women currently engaged in a structured exercise program