1463Impact of missing outcome data in meta-analyses of lifestyle interventions during pregnancy to reduce postpartum-weight-retention

Abstract

Background High risk of bias associated with missing outcome data (MOD) in meta-analyses (MAs) of the effects of lifestyle interventions during pregnancy on postpartum weight retention (PPWR), casts doubt on whether such interventions can be relied upon as truly effective, since estimates are deemed valid only if MOD was missing at random (MAR). Methods We conducted a systematic overview of MAs to examine the impact of MOD on the estimation of meta-analytic summary intervention effects and conducted sensitivity analyses using pattern mixture models and informative missingness parameters (describing how the outcome in the missing participants may be related to the outcome in the completers), to ascertain the robustness of the estimates to reasonable deviations from the MAR assumption. Results Three relevant MAs were identified, all with high MOD rates in the RCTs included (median>30%), and all reporting beneficial intervention effects on PPWR (in kg) estimated based on complete case analyses: [-0.78 (95%CI: -1.39,-0.16), -0.81 (-1.57,-0.06), and -0.94 (-1.52,-0.37)] in MAs of any lifestyle, exercise, or diet + exercise interventions, respectively. In plausible scenarios where the outcome for the intervention group in participants with vs without MOD was worse (by 0.5kg), effect estimates were attenuated in all and no longer significant in 2 of the MAs [-0.58 (-1.29,0.13), -0.70 (-1.50,0.10) and -0.88 (-1.73,-0.02)]. Conclusions Statistical significance was retained when all 19 RCTs identified across MAs were meta-analysed: -0.63 (-0.17,-0.08). Key messages The clinical relevancy of effects of this magnitude remains unclear.