Page 163 - Pro-active Management of Women’s Health after Cardiometabolic Complicated Pregnancies

3.5 Feasibility and effectiveness of a lifestyle intervention| 161
proportion of eligible women that completed the intervention was at least 11%. The primary outcome measure for effectiveness was change in weight before and after the intervention. If the lifestyle intervention would be effective in improving diet and exercise, it would result in weight loss. Weight, as part of Body Mass Index (BMI) is a major risk factor of cardiometabolic disease. A weight loss of 2.7 kg, corresponding with a risk reduction of 50% for diabetes mellitus after 4 years, was considered clinically relevant 58 277. With mean weight loss in the intervention group of 3.5 kg (SD 5.5), mean weight loss in the control group of 0.8 kg (SD 4.4)277, α 0.05 (2-sided), β 0.80 and a cases-to-control ratio of 2:1 and an expected drop-out rate of 30% we calculated a sample size of 108 cases and 54 controls. Secondary outcome measures included the other
anthropometrical, biochemical and lifestyle measurements.
Based on the intention-to-treat principle, women who became pregnant
during the study period were considered as drop-out. Their pregnancy would have had considerable influence on the outcome measures. Women who dropped out for other reasons were approached for the final visit at 13 months postpartum.
Statistical analyses were performed using IBM SPSS Statistics, version 20, International Business Machines Corp©. The weight change between six months postpartum and the end of the study at 13 months postpartum was calculated for each participant in the intervention and control group. Using a linear regression model with weight change as outcome variable, we used the regression coefficient of the case group as effect of the intervention and thus adjusted for normal or ‘background’ change in the control group that would supposedly have occurred if lifestyle intervention had not been conducted (model 1). We also adjusted for known confounders (baseline weight measure at start at 6 months postpartum, duration of breastfeeding), and significantly