OBJECTIVE: Estimating physical activity levels (PAL) is difficult outside of the laboratory, and patient-reported PAL are often overestimated. Herein, we determine the importance of selecting the correct PAL when computing estimated energy requirements (EER) to determine gestational weight gain (GWG). Then, we examine whether data from a wearable can be used to select PAL and predict EER. METHODS: PAL were measured at early and late pregnancy among 53 pregnant female individuals (BMI >
30 kg/m RESULTS: PAL decreased from early to late pregnancy (p = 0.01). When simulating the effect of overestimating physical activity on EER in late pregnancy, excess GWG occured in all individuals (p <
0.001) with decreased PAL during pregnancy. Average daily step counts and activity minutes in early and late pregnancy overlapped across PAL and are not recommended for use. CONCLUSIONS: Step count and activity minute data from wearables cannot be used to determine PAL in pregnant individuals with obesity. To minimize excess GWG risks, our outcomes suggest assuming "inactive" physical activity when estimating EER for pregnant people with obesity.