Review Physical Activity Interventions in Pregnancy and Risk of Gestational Diabetes Mellitus A Systematic Review and Meta-analysis Lindsey M. Russo, BS, Carrie Nobles, MPH, Karen A. Ertel, PhD, MPH, Lisa Chasan-Taber, ScD, MPH, and Brian W. Whitcomb, PhD OBJECTIVE: Gestational diabetes mellitus (GDM) is a com- mon complication of pregnancy associated with an increased incidence of pregnancy complications, adverse pregnancy outcomes, and maternal and fetal risks of chronic health conditions later in life. Physical activity has been proposed to reduce the risk of GDM and is supported by observational studies, but experimental research assess- ing its effectiveness is limited and conflicting. We aimed to use meta-analysis to synthesize existing randomized con- trolled studies of physical activity and GDM. DATA SOURCES: We searched MEDLINE, Cochrane Central Register of Controlled Trials, and ClinicalTrials. gov for eligible studies. METHODS OF STUDY SELECTION: The following com- bination of keywords was used: (pregnant or pregnancy or gestation or gestate or gestational or maternity or maternal or prenatal) AND (exercise or locomotion or activity or training or sports) AND (diabetes or insulin sensitivity or glucose tolerance) AND (random* or trial). Eligibility was restricted to studies that randomized participants to an exercise-only-based intervention (ie, separate from dietary interventions) and presented data regarding GDM risk. Two authors performed the data- base search, assessment of eligibility, and abstraction of data from included studies, and a third resolved any discrepancies. A total of 469 studies was retrieved, of which 10 met inclusion criteria and could be used for analysis (3,401 participants). TABULATION, INTEGRATION, AND RESULTS: Fixed- effects models were used to estimate summary relative risk (RR) and 95% confidence interval (CI) and I 2 to assess heterogeneity. There was a 28% reduced risk (95% CI 9–42%) in the intervention group compared with the control group (RR 0.72, P5 .005). Heterogeneity was low (I 2 512%) and nonsignificant (P5 .33). CONCLUSION: The results from this meta-analysis sug- gest that physical activity in pregnancy provides a slight protective effect against the development of GDM. Studies evaluating type, timing, duration, and compli- ance of physical activity regimens are warranted to best inform obstetric guidelines. (Obstet Gynecol 2015;125:576–82) DOI: 10.1097/AOG.0000000000000691 G estational diabetes mellitus (GDM), defined as carbohydrate intolerance with the onset or first recognition during pregnancy, 1 affects an estimated 2–10% of pregnancies in the United States 2 with rates varying by population subgroup and diagnostic test utilized. Prevalence of GDM varies by race–ethnicity, ranging from a low of 6.8% among non-Hispanic whites to 16.3% among Asians and Pacific Islanders. 3 Data have suggested that the incidence of GDM is increasing in all race–ethnicities in the United States, a trend paralleling the increase in prevalence of type 2 diabetes. 2 Gestational diabetes mellitus is associated with increased risk of fetal macrosomia, large-for- gestational-age neonates, preeclampsia, perinatal mor- tality, and cesarean delivery 4–6 as well as long-term hazards, including a higher risk of maternal type 2 diabetes and obesity, 7 glucose intolerance, and meta- bolic syndrome in the offspring of women born to mothers diagnosed with GDM. 8 Established risk factors for GDM include a history of GDM in a prior pregnancy, 9 history of delivering a macrosomic neonate, 10 advanced maternal age, 9 From the Division of Biostatistics and Epidemiology, University of Massachu- setts, Amherst, Massachusetts. Corresponding author: Brian W. Whitcomb, PhD, Division of Biostatistics and Epidemiology, University of Massachusetts, 715 N. Pleasant Street, Amherst, MA 01002; e-mail: bwhitcomb@schoolph.umass.edu. Financial Disclosure The authors did not report any potential conflicts of interest. © 2015 by The American College of Obstetricians and Gynecologists. Published by Wolters Kluwer Health, Inc. All rights reserved. ISSN: 0029-7844/15 576 VOL. 125, NO. 3, MARCH 2015 OBSTETRICS & GYNECOLOGY Copyright ª by The American College of Obstetricians and Gynecologists. Published by Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.