Early Testing of a Mobile App‐Based Intervention to Support Body Weight Awareness and Monitoring in Pregnancy: A Randomised Controlled Feasibility Trial ( BUMP2.0 )

ABSTRACT Aims To assess the feasibility of a mobile app‐based intervention to support gestational weight gain awareness and monitoring. Materials and Methods A total of 157 women aged ≥ 18 years, at < 20 weeks' gestation, were randomised 2:1 to an intervention ( n = 107) or control group ( n = 50), and followed‐up until late pregnancy (34 weeks' gestation to delivery). The intervention was a mobile app encouraging weekly self‐weighing and gestational weight gain tracking, offering feedback relative to Institute of Medicine (IOM) recommendations and signposting to online resources. The control group received usual antenatal care. Feasibility outcomes assessed retention and app engagement. Weight change and the proportion exceeding the IOM‐recommended upper weekly weight gain rate were also assessed. Intervention participants reported their experiences through open‐ended survey responses and qualitative interviews. Results 106 participants provided follow‐up weight data; a retention rate of 67.5% (95% CI: 59.9 to 74.4). A total of 60.7% (95% CI: 51.3 to 69.5) of intervention participants logged a weight in at least half of their participation weeks, with 63.6% (95% CI: 54.1 to 72.1) spontaneously logging a weight in late pregnancy, meeting progression criteria. Median (IQR) body mass index at entry was 25.8 (23.3–29.6) kg/m 2 . During a median (IQR) of 25.6 (22.3–29.3) weeks in the study, mean (SD) weight gain was 9.2 (5.1) kg in the intervention group and 9.9 (4.0) kg in controls (adjusted between‐group difference: −0.7 kg [95% CI: −2.5 to 1.2]), with 63.4% (95% CI: 51.8 to 73.6) of intervention and 60.0% (95% CI: 43.6 to 74.5) of control participants exceeding the IOM‐recommended weekly weight gain rate. Most intervention participants valued weight tracking and the app's ease of use, but some reported anxiety and wanted more detailed guidance and support for weight management. Conclusions App‐supported regular self‐weighing during pregnancy met the pre‐specified progression criteria and was generally acceptable to participants. Exploratory analyses showed no significant between‐group differences in gestational weight gain, though the magnitude was noticeable for such a low‐intensity intervention. Interviews with women highlighted opportunities for improvements through more personalised feedback and support. Trial Registration NCT06882837