Participants (n=12) were on average 16.8 [standard deviation (SD): 2.0] weeks gestation with average pre-pregnancy body mass index of 30.5 (SD: 4.8) kg/m2. Participant retention was 92% (n=11). Participants logged into the website a median of 21 times [interquartile range (IQR), 8-37; range, 2-98] over 12 weeks, and 58% (n=7) logged into the website during the last week of the intervention. All participants said they would be very likely or likely to participate again, and 100% said they would be very likely or likely to recommend the intervention to a pregnant friend. In post-intervention interviews, 64% (n=7) explicitly said that the website was easy to use, but 100% (n=11) mentioned usability issues. When asked their preferred intervention platform, 18% (n=2) somewhat or strongly preferred a private website, 18% (n=2) had no preference, and 64% (n=7) somewhat or strongly preferred Facebook. Seventy percent (n=7) had excessive gestational weight gain, 10% (n=1) inadequate gestational weight gain, and 20% (n=2) gained within recommended ranges.