A Cochrane review [Abstract] 1 included 14 studies involving a total of 1 014 women. Of the 9 studies reporting on physical fitness, 6 reported significant improvement in physical fitness in the exercise group, although inconsistencies in summary statistics and measures used to assess fitness prevented quantitative pooling of results. 11 studies reported on pregnancy outcomes. A pooled increased risk of preterm birth (RR 1.82, 95% CI 0.35 to 9.57) with exercise, albeit statistically nonsignificant, does not cohere with the absence of effect on mean gestational age (MD +0.10, 95% CI -0.11 to +0.30 weeks), while the results bearing on growth of the fetus are inconsistent. One small trial reported that physically fit women who increased the duration of exercise bouts in early pregnancy and then reduced that duration in later pregnancy gave birth to larger infants with larger placentas.
A systematic review 2 included 61 RCTs. The evidence for a benefit of combined exercise (aerobic+resistance) interventions on maternal cardiorespiratory fitness and prevention of urinary incontinence was strong. A weak or insufficient level of evidence was found for the rest of interventions and outcomes.
A meta-analysis 3 included 23 RCTs with a total of 4462 pregnant women. Compared with women having conventional medical care, gestational weight gain was significantly decreased in women with physical exercise (weighted mean difference [WMD] -1.02, 95% CI -1.35 to -0.70; P < .01; I = 48.4%]. Women appeared to benefit more for gestational weight control of exercise frequency of 3 times per week (WMD -1.22, 95% CI -1.55 to -0.90; I = 40.3%) and exercise duration of 30 to 45 minutes each time (WMD -1.32, 95% CI -1.79 to -0.85; I = 1.5%).
Another Cochrane review [Abstract] 1 included 49 studies with a total of 11 444 subjects. Diet or exercise, or both, interventions reduced the risk of excessive gestational weight gain on average by 20% overall (high-quality evidence). Interventions involving low glycaemic load diets, supervised or unsupervised exerciseonly, or diet and exercise combined all led to similar reductions in the number ofwomen gaining excessive weight in pregnancy. However, there was no significant difference between intervention and control groups with regard to pre-eclampsia, caesarean delivery, preterm birth overall, infant macrosomia, or poor neonatal outcomes including shoulder dystocia, neonatal hypoglycaemia, hyperbilirubinaemia, or birth trauma.
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