Of the 710 women with GDM, 695 (97.9%) were contacted (). Of these, 318 completed the eligibility screening. There were no differences between these two groups with regard to age, race/ethnicity, and gestational age (data not shown). Among those who completed the eligibility screening, 83 (23.1%) were not eligible. Among the remaining 235 women, 222 (94.5%) agreed to participate and made a baseline visit appointment; 197 (83.8%) women attended the baseline visit, gave informed consent, and were randomized. Participant retention at each follow-up visit in the intervention and usual care conditions, respectively, were as follows: 95 and 97% at 6 weeks, 80 and 91% at 7 months, and 80 and 90% at 12 months postpartum (Fig. 1). No differences in baseline characteristics were observed between women in the intervention and usual care conditions except that the 1-h glucose value from the diagnostic 100-g oral glucose tolerance test was lower among women in the intervention condition compared with women in the usual care condition and small differences in smoking and employment status ().
Flow chart of participant recruitment and retention, Kaiser Permanente Northern California, 2005–2009.
Baseline characteristics of women with GDM by randomization condition, KPNC, 2005–2008
The proportion of women who reached their postpartum weight goal was higher in the intervention condition (). Although this difference was not statistically significant, the condition difference in absolute proportion was 16.1% (P = 0.07) at 12 months postpartum. Similar results were obtained after adjusting for 1-h glucose levels and in subgroup analyses where women were stratified by smoking or employment status (data not shown).
Proportion of women with GDM meeting the postpartum weight goals by randomization group and time since delivery
Because the postpartum weight goals differed between women with pregravid BMI <25.0 kg/m2 and women with pregravid BMI ≥25.0 kg/m2, the efficacy of the intervention within these two groups was examined (). The magnitude of the absolute condition difference in the proportion of women meeting the postpartum weight goal was similar in normal weight and overweight/obese women. Because the rationale for starting the intervention during pregnancy was that preventing excessive GWG would result in reduced postpartum weight retention, the efficacy of the intervention was assessed separately in those who did and did not exceed the recommended GWG (). The intervention appeared to be more effective among women who did not exceed the guidelines for GWG; the absolute difference between the intervention and the usual care conditions in the proportion of women reaching the weight goal at 12 months postpartum was 22.5% (P = 0.04).
In a sensitivity analysis where women who did not attend the postpartum visits were categorized as not having reached the weight goal at 12 months postpartum, the intervention condition remained more likely to reach the postpartum weight goal than usual care (absolute difference = 11%) despite a slightly greater loss to follow-up among women in the intervention condition.
As compared with the usual care arm, the women in the intervention at 7 months postpartum showed a statistically significant decrease in dietary fat intake (condition difference in the mean change in percent of calories from fat: −3.55%, P = 0.002); a greater but nonsignificant increase in physical activity (condition difference in the mean change in minutes of moderate-to-vigorous physical activity per week: 25.3, P = 0.91); and a higher but not significant likelihood to partially or exclusively breastfeed (condition difference in proportion: 15.0%, P = 0.09) ().
Breastfeeding and changes in dietary fat intake and physical activity by randomization condition and time since delivery
Process measures of the intervention
Ninety-three percent of the women randomized to the intervention completed the first prenatal session, and 79% completed two or more. On average, the pregnancy telephone sessions lasted 31.2 ± 17.7 min, while the in-person sessions lasted approximately 1 h. For the early postpartum phase, 74% of the women completed the 8 core intervention sessions. Overall, women completed an average of 9.4 (SD 4.4) postpartum sessions. The telephone sessions lasted on average 32.6 ± 15.7 min each, while the in-person sessions lasted approximately 1 h. Women returned a median of 3 self-monitoring diaries, with 30.9% returning 6 or more. Overall, the women were very satisfied with the intervention (97%) and most (92%) would recommend the program to others with GDM. A majority (82%) said they were likely to continue to set weight goals.
Focus groups with intervention women
Two focus groups, each with 8 intervention participants, were conducted upon completion of the study. Women reported the desire for more information regarding health risks after GDM. For physical activity, the following themes emerged: 1) the need for support for physical activity from family and others in their social network; 2) the addition of a website to connect with other GDM women; and 3) tips on how to exercise with a new infant. Reported barriers to physical activity were personal and child illnesses, returning to work, and bad weather. For diet, the following themes emerged: 1) the need for information on the optimal type of carbohydrate for the transition from the pregnancy diet to the low-fat postpartum diet and 2) the need for low-fat recipes.