Antenatal exercise in overweight and obese women and its effects on offspring and maternal health: design and rationale of the IMPROVE (Improving Maternal and Progeny Obesity Via Exercise) randomised controlled trial.

BACKGROUND: Obesity during pregnancy is associated with adverse outcomes for the offspring and mother. Lifestyle interventions in pregnancy such as antenatal exercise, are proposed to improve both short- and long-term health of mother and child. We hypothesise that regular moderate-intensity exercise during the second half of pregnancy will result in improved maternal and offspring outcomes, including a reduction in birth weight and adiposity in the offspring, which may be protective against obesity in later life.

METHODS/DESIGN: The IMPROVE (Improving Maternal and Progeny Risks of Obesity Via Exercise) study is a two-arm parallel randomised controlled clinical trial being conducted in Auckland, New Zealand. Overweight and obese women (BMI ≥25 kg/m2) aged 18-40 years, with a singleton pregnancy of <20 weeks of gestation, from the Auckland region, are eligible for the trial. Exclusion criteria are ongoing smoking or medical contra-indications to antenatal exercise.Participants are randomised with 1:1 allocation ratio to either intervention or control group, using computer-generated randomisation sequences in variable block sizes, stratified on ethnicity and parity, after completion of baseline assessments. The intervention consists of a 16-week structured home-based moderate-intensity exercise programme utilising stationary cycles and heart rate monitors, commencing at 20 weeks of gestation. The control group do not receive any exercise intervention. Both groups undergo regular fetal ultrasonography and receive standard antenatal care. Due to the nature of the intervention, participants are un-blinded to group assignment during the trial.The primary outcome is offspring birth weight. Secondary offspring outcomes include fetal and neonatal body composition and anthropometry, neonatal complications and cord blood metabolic markers. Maternal outcomes include weight gain, pregnancy and delivery complications, aerobic fitness, quality of life, metabolic markers and post-partum body composition.

DISCUSSION: The results of this trial will provide valuable insights on the effects of antenatal exercise on health outcomes in overweight and obese mothers and their offspring.

TRIAL REGISTRATION: Australian New Zealand Clinical Trials Registry ACTRN12612000932864.