Original Research Pregnancy Exercise and Nutrition With Smartphone Application Support A Randomized Controlled Trial Maria A. Kennelly, MRCPI, Kate Ainscough, MSc, Karen L. Lindsay, PhD, Elizabeth O’Sullivan, PhD, Eileen R. Gibney, PhD, Mary McCarthy, PhD, Ricardo Segurado, PhD, Giuseppe DeVito, PhD, Orla Maguire, PhD, Thomas Smith, PhD, Mensud Hatunic, MD, and Fionnuala M. McAuliffe, MD, FRCOG OBJECTIVE: To evaluate the effect of a healthy lifestyle package (an antenatal behavior change intervention supported by smartphone application technology) on the incidence of gestational diabetes mellitus (GDM) in overweight and obese women. METHODS: Women with body mass indexes (BMIs) 25– 39.9 were enrolled into this randomized controlled trial. The intervention consisted of specific dietary and exer- cise advice that addressed behavior change supported by a tailor-designed smartphone application. Women in the control group received usual care. The primary outcome was the incidence of GDM at 28–30 weeks of gestation. To reduce GDM from 15% to 7.2%, we estimated that 506 women would be required to have 80% power to detect this effect size at a significance of .05, that is, 253 in each group. RESULTS: Between March 2013 and February 2016, 565 women were recruited with a mean BMI of 29.3 and mean gestational age of 15.5 weeks. The incidence of GDM did not differ between the two groups, 37 of 241 (15.4%) in the intervention group compared with 36 of 257 (14.1%) in the control group (relative risk 1.1, 95% CI 0.71–1.66, P5 .71). CONCLUSIONS: A mobile health-supported behavioral intervention did not decrease the incidence of GDM. CLINICAL TRIAL REGISTRATION: ISRCTN registry, https://www.isrctn.com/, ISRCTN29316280. (Obstet Gynecol 2018;0:1–9) DOI: 10.1097/AOG.0000000000002582 G estational diabetes mellitus (GDM) is “glucose intolerance first recognized during pregnancy” 1 and is associated with up to a 70% risk of type 2 diabetes in later life. 2 A family history of type 2 dia- betes, maternal adiposity, and excess gestational weight gain seem to confer the greatest risk. 3,4 Despite pregnancy being considered a “teachable moment,” overweight and obese women often find it difficult to change dietary and physical activity behaviors dur- ing pregnancy. 5 Recently published studies describing combined nutrition and exercise interventions have reported only some success in reducing GDM. 2,6–9 The reason for this could be attributed to the lack of emphasis on psychologic theories in their methodol- ogies that are imperative for changing lifestyle behav- iors in an already potentially unmotivated group. Therefore, it is now recommended that lifestyle inter- ventions should incorporate behavior change theories into study design and methodology. 10 From the UCD Perinatal Research Centre, Obstetrics and Gynaecology, School of Medicine, the UCD Institute of Food and Health, UCD CSTAR, and the School of Public Health, Physical & Sports Sciences, Health Sciences Centre, University College Dublin, Dublin, the Department of Management & Marketing, Univer- sity College Cork, Cork, and the Department of Endocrinology, St. Vincent’s University Hospital, and the Department of Endocrinology, National Maternity Hospital, Dublin, Ireland. This trial was funded by the National Maternity Hospital medical fund. The funding source did not have a role in the trial design or manuscript preparation. Presented at the Society for Reproductive Investigation, March 15–18, 2017, Orlando, Florida; and at the British Society for Maternal Fetal Medicine, March 30–31, 2017, Amsterdam, the Netherlands. The authors thank the mothers of the National Maternity Hospital who partic- ipated in the study. Each author has indicated that he or she has met the journal’s requirements for authorship. Corresponding author: Fionnuala M. McAuliffe, FRCOG, FRCPI, Chair and Professor of Obstetrics & Gynaecology, University College Dublin Head, Women’s and Children’s Health, University College Dublin University College Dublin, National Maternity Hospital, Holles Street, D2, Dublin, Ireland; email: fionnuala.mcauliffe@ucd.ie. Financial Disclosure The authors did not report any potential conflicts of interest. © 2018 by American College of Obstetricians and Gynecologists. Published by Wolters Kluwer Health, Inc. All rights reserved. ISSN: 0029-7844/18 Copyright Ó by American College of Obstetricians and Gynecologists. Published by Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited. VOL. 0, NO. 0, MONTH 2018 OBSTETRICS & GYNECOLOGY 1