The effect of model specification on multiply imputed data: lessons learned from Project DC-HOPE

The District of Columbia Healthy Outcomes of Pregnancy Education (DC-HOPE) project is a randomized trial funded by the National Institute of Child Health and Human Development to test the effectiveness of an integrated education and counseling intervention (INT) versus usual care (UC) to reduce four risk behaviors among pregnant women. Participants were interviewed at baseline and three additional time points. Multiple imputation (MI) was used to estimate data for missing interviews. MI was done twice: once with all data imputed simultaneously, and once with data for women in the INT and UC groups imputed separately. Analyses of both imputed data sets and the pre-imputation data are compared.