**Background:** Excessive gestational weight gain (GWG) is associated with negative maternal and infant outcomes including gestational diabetes, hypertensive disorders, macrosomia, and postpartum weight retention. Over half of women with pre-pregnancy overweight and 6 in 10 with obesity gain more than recommended. While lifestyle interventions reduce GWG by about 1 kg, most rely on in-person visits, which pose barriers for pregnant women. Digital health approaches may overcome these barriers, but meta-analyses of digital GWG interventions have not shown significant reductions in GWG. This study aimed to develop and assess the feasibility of a web-based GWG intervention for women with pre-pregnancy overweight or obesity.
**Methods:** The intervention was developed using a user-centered design approach, incorporating formative interviews (n=15 pregnant women) and usability testing (n=8 pregnant women, two rounds). The final 12-week intervention included an online discussion board with coaches and peers, an interactive weight gain tracker with IOM reference lines, and a list of online resources. The one-arm pilot study enrolled 12 women (≥18 years, singleton gestation <20 weeks, pre-pregnancy BMI 25–45 kg/m², active Facebook users). Participants attended a baseline assessment, engaged in the 12-week intervention, and completed a follow-up assessment including a semi-structured interview. Feasibility outcomes were recruitment, retention, engagement (logins, forum posts, weights logged), acceptability, and website usability (System Usability Scale [SUS] and qualitative interviews). GWG was an exploratory outcome abstracted from obstetric records.
**Key Results:** Of 27 women screened, 18 were eligible (67%), and 12 enrolled. Retention was 92% (n=11). Participants (n=12) had a mean age of 31.7 (SD: 5.5) years, mean gestational age of 16.8 (SD: 2.0) weeks, and mean pre-pregnancy BMI of 30.5 (SD: 4.8) kg/m² (50% overweight, 50% obesity). Over 12 weeks, participants logged in a median of 21 times (IQR: 8–37; range: 2–98), made a median of 24.5 forum posts (IQR: 4–31.5; range: 0–81), and logged a median of 2.5 weights (IQR: 0–8.5; range: 0–19). Fifty-eight percent (n=7) logged in during week 12. All participants said they would be very likely or likely to participate again and recommend the program. The median SUS score was 75 (IQR: 67.5–97.2; range: 60–100); 45% (n=5) rated the website as highly usable (>80). However, 100% (n=11) mentioned usability issues (e.g., cumbersome on smartphones, duplicate posts from slow refresh rates). When asked about platform preference, 64% (n=7) somewhat or strongly preferred a private Facebook group, 18% (n=2) preferred a private website, and 18% (n=2) had no preference. Among the 10 women who delivered at UMMMC, 70% (n=7) had excessive GWG, 10% (n=1) inadequate, and 20% (n=2) within recommended ranges. Among those with pre-pregnancy overweight, 60% (n=3) gained excessively; among those with obesity, 80% (n=4) gained excessively.
**Clinical Implications:** This pilot study demonstrated that a web-based GWG intervention is feasible and acceptable, with high retention and participant satisfaction. However, universal usability issues and a 70% rate of excessive GWG highlight the need for further development before efficacy testing. The strong participant preference for a commercial social media platform (Facebook) over a researcher-built website suggests that future interventions should consider leveraging existing platforms to improve engagement and usability. The study also underscores the difficulty of preventing excessive GWG, even among motivated volunteers, and the importance of engaging women early in pregnancy or pre-conception. Limitations include the small sample, lack of a control group, and a more educated sample than the general US birthing population.