BACKGROUND: Maternal metabolic health during the prenatal period is an established determinant of cardiometabolic disease risk. Many studies have focused on poor offspring outcomes after exposure to poor maternal health, while few have systematically appraised the evidence surrounding the role of maternal exercise in decreasing this risk. The aim of this study is to characterize and quantify the specific impact of prenatal exercise on children's cardiometabolic health markers, at birth and in childhood. METHODS: A systematic review of Scopus, Medline, Embase, CENTRAL, CINAHL, and SPORTDiscus up to December 2017 was conducted. Randomized controlled trials (RCTs) and prospective cohort studies of prenatal aerobic exercise and/or resistance training reporting eligible offspring outcomes were included. Four reviewers independently identified eligible citations and extracted study-level data. The primary outcome was birth weight; secondary outcomes, specified a priori, included large-for-gestational age status, fat and lean mass, dyslipidemia, dysglycemia, and blood pressure. We included 73 of the 9804 citations initially identified. Data from RCTs was pooled using random effects models. Statistical heterogeneity was quantified using the I2 test. Analyses were done between June and December 2017 and the search was updated in December 2017. RESULTS: Fifteen observational studies (n = 290,951 children) and 39 RCTs (n = 6,875 children) were included. Observational studies were highly heterogeneous and had discrepant conclusions, but globally showed no clinically relevant effect of exercise on offspring outcomes. Meta-analyzed RCTs indicated that prenatal exercise did not significantly impact birth weight (mean difference (MD) -22.1 g, 95% confidence interval (CI) -51.5 to 7.3 g, n = 6,766) or large-for-gestational age status (risk ratio 0.85, 95% CI 0.51 to 1.44, n = 937) compared to no exercise. Sub-group analyses showed that prenatal exercise reduced birth weight according to timing (starting after 20 weeks of gestation MD -84.3 g, 95% CI -142.2 to -26.4 g, n = 1,124), type of exercise (aerobic only MD -58.7 g, 95% CI -109.7 to -7.8 g; n = 2,058), pre-pregnancy activity status (previously inactive MD -34.8 g, 95% CI -69.0 to -0.5 g; n = 2,829), and exercise intensity (light to moderate intensity only MD -45.5 g, 95% CI -82.4 to -8.6 g; n = 2,651). Fat mass percentage at birth was not altered by prenatal exercise (0.19%, 95% CI -0.27 to 0.65%; n = 130); however, only two studies reported this outcome. Other outcomes were too scarcely reported to be meta-analyzed. CONCLUSIONS: Prenatal exercise does not causally impact birth weight, fat mass, or large-for-gestational-age status in a clinically relevant way. Longer follow up of offspring exposed to prenatal exercise is needed along with measures of relevant metabolic variables (eg, fat and lean mass). PROTOCOL REGISTRATION: Protocol registration number CRD42015029163.

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