Erratum to: Study protocol: differential effects of diet and physical activity based interventions in pregnancy on maternal and fetal outcomes: individual patient data (IPD) meta-analysis and health economic evaluation. Issue 1 (December 2015) - Ruifrok, Anneloes; Rogozinska, Ewelina; van Poppel, Mireille; Rayanagoudar, Girish; Kerry, Sally; de Groot, Christianne; Yeo, SeonAe; Molyneaux, Emma; Barakat Carballo, Ruben; Perales, Maria; Bogaerts, Annick; Cecatti, Jose; et al.