There is not enough evidence to recommend any intervention for preventing excessive weight gain during pregnancy, due to the significant methodological limitations of included studies and the small observed effect sizes. More high-quality randomised controlled trials with adequate sample sizes are required to evaluate the effectiveness of potential interventions.
Aerobic exercise and submaximal functional capacity in overweight pregnant women: a randomized trial.
To evaluate the effects of aerobic training on submaximal cardiorespiratory capacity in overweight pregnant women.
                We conducted a randomized clinical trial in a referral center prenatal clinic during the period 2000-2002. Of 132 overweight (body mass index 26-31 kg/m2) but otherwise healthy volunteers, at 20 years of age or older, with gestational age of 20 weeks or less, and without diabetes or hypertension, 92 consented to participate and were randomized. Intervention consisted of 3 one-hour aerobic exercise sessions per week; the control group received weekly relaxation and focus group discussions. The main outcome measure was submaximal exercise capacity evaluated by oxygen uptake at the anaerobic (first ventilatory) threshold during cardiopulmonary treadmill testing 12 weeks after randomization.
                Oxygen uptake at the anaerobic threshold increased 18% (15.9 +/- 2.6 to 18.1 +/- 3.1 mL . min(-1) . kg(-1)) in the exercise group but decreased 16% (16.9 +/- 3.0 to 15.8 +/- 2.6 mL . min(-1) . kg(-1)) among the control group. Oxygen consumption at the anaerobic threshold, adjusted through analysis of covariance for baseline oxygen uptake, was 2.68 (95% confidence interval 1.23 to 4.12) mL . min(-1) . kg(-1) greater in the exercise group. Women in the exercise group were approximately 5 times more likely than those in the control group to have regular or good cardiorespiratory capacity (12/38 versus 2/38; relative risk 5.2, 95% confidence interval 1.2 to 22.0, number needed to treat 5).
                Aerobic training in overweight pregnant women substantially increases submaximal exercise capacity, overcoming the otherwise negative effects of pregnancy in this regard. Additional studies are required to evaluate its effect on major clinical outcomes.