Objective: To evaluate temporal trends in total gestational weight gain (GWG) from 2007 to 2019 in a large pregnancy cohort. Design: Prospective cohort study. Setting: LIFECODES study, Brigham and Women’s Hospital, Boston, MA. Sample: 3,675 pregnant participants, with 29,037 weight measures. Methods: Using self-reported pre-pregnancy weight and serial weight measurements, we applied a mixed effects model to predict maternal weight at delivery. Total GWG (kg) was defined as the difference between predicted delivery weight and pre-pregnancy weight, classified based on the 2009 guidelines by pre-pregnancy BMI. Main Outcome Measures: Trends in proportions of GWG categories, both overall and stratified by maternal characteristics; Trends in covariate-adjusted geometric means (GMs) of GWG. Results: The proportion of participants with total GWG within the guidelines decreased from 46% in 2007-2008 to 24% in 2018-2019, which was driven by an increase in those gaining above the guidelines (40% to 73%). Trends were consistent across maternal characteristics, though the largest relative increases of proportions above the guidelines were observed among those of normal pre-pregnancy BMI (19% to 62%) and of non-Hispanic Black (48% to 85%) or non-Hispanic White (37% to 74%) race/ethnicity. Adjusted GMs increased from 8.3 kg (95% confidence interval [CI]: 6.3, 10.8) in 2007-2008 to 10.9 kg (95% CI: 7.9, 14.9) in 2018-2019. Conclusions: Over time, fewer women have been meeting the revised 2009 GWG guidelines, and this trend is driven by increasing proportions of pregnant individuals gaining weight above the recommendations.