Metabolic rate and modifications to the thermal comfort model for pregnant women at a hospital in Xi’an, China

The accurate prediction of thermal sensation for pregnant women is not achievable with existing predicted mean vote (PMV) models, likely due to alterations in metabolic rate associated with gestation. Existing studies and standards lack data on the metabolic rates of pregnant women in China across trimesters, making it impossible to verify whether deviations in the PMV model are associated with changes in metabolic rate. This study recruited 30 women with pre-pregnancy normal body mass index (BMI) at different gestational stages. Indirect calorimetry measured sitting-still metabolic rate and respiratory parameters, and the PMV model was modified based on actual metabolic rates. Results indicate that the sitting-still metabolic rates of 0.86, 1.06 and 1.21 met were measured for pregnant women, corresponding to the three pregnancy stages in order. Metabolic rates differed significantly between the first and third trimesters of pregnancy ( p < 0.01). The modified model (termed PMV m ), which incorporated measured metabolic rates, showed a 22% improvement in accuracy during the third trimester, with no significant effect in the first or second trimesters. These findings contribute to the refinement of thermal comfort theory for pregnant women, offering data references to improve the precision of thermal model predictions.