Prenatal Metabolism Tracking: A Case Series Report of the Portable Breezing Device
Authors: Wyst Kiley Vander , Whisner Corrie M. 
Published: November 2023

BackgroundMetabolism changes significantly during pregnancy. Despite an increased need for calories, excessive gestational weight gain affects many women. This increase in weight often contributes to adverse maternal and infant health outcomes. Total energy expenditure consists of physical activity (<15%), thermogenesis (~10%), and resting energy expenditure (REE, >75%). REE cannot be measured by existing accelerometer‐based devices and current measurement technologies are bulky, expensive and complicated.ObjectivesTo evaluate caloric needs during pregnancy in real‐time among four pregnant women using a portable device which measures resting energy expenditure.MethodsREE, physical activity, and weight were self‐assessed in three pregnant women from pregnancy onset through delivery using personal health‐tracking devices. The women used the Breezing™ device which measures energy expenditure via indirect calorimetry. Each woman breathed through a disposable mouthpiece for about 1 to 2 minutes or until a total of 6 liters of exhaled air was collected by the Breezing device. The rates of oxygen consumption and carbon dioxide release were determined by a proprietary sensor cartridge and a flow meter. Data were transferred from the device to a mobile phone application where it was processed and made visually available to the participants. Physical activity was assessed via commercially available devices per participant preference (Fitbit™, Withings™ and Health™phone applications). Weight was assessed using a digital Withings™ scale.ResultsCase 1 had a baseline REE of 1200 and postpartum REE of 1540 kCal/day. REE increased during the 2nd trimester and then remained relatively stable. Case 1 had a baseline weight of 44 kg, a total weight gain of 13.1 kg, and a postpartum weight loss of 6.4 kg. She averaged 3730 (±1980) steps per week and an average caloric intake of 2200 during pregnancy. Case 2 had a baseline REE of 1520 and postpartum REE of 1250 kCal/day. REE remained steady throughout pregnancy with an average of 1520±110 kCal/day, suggesting minimal fluctuation. Case 2 had a baseline weight of 60 kg, a total weight gain of 15.3 kg, and a postpartum weight loss of 13.3 kg. She averaged 5720 (±2030) steps per week and an average caloric intake of 1860 calories during pregnancy. Case 3 had a baseline REE of 1625 and postpartum REE of 1195 kCal/day. REE dropped by 485±110 kCal/day. Case 3 had a baseline weight of 51.4 kg, a total weight gain of 5.9 kg, and a postpartum weight loss of 5.9 kg. She averaged 6690 (±5315) steps per week and an average caloric intake of 1870 calories during pregnancy. Case 4 had a baseline REE of 1200 and postpartum REE of 1400 kCal/day. REE varied throughout pregnancy with an average increase of 279± 88 kCal/day. Case 4 had a baseline weight of 52.2 kg, a total weight gain of 18.5 kg, and a postpartum weight loss of 11.6 kg. She averaged 4985 (±2180) steps per week and an average caloric intake of 2550 calories during pregnancy.ConclusionREE is a complex health factor that depends on several individual aspects. It can increase (Cases 1 and 4), remain constant (Case 2), or decrease (Case 3) during pregnancy. Energy expenditure has great individual variation. This warrants further investigation into how metabolism tracking during pregnancy may influence the risk for excessive gestational weight gain and can be used by clinicians for real‐time intervention.Support or Funding InformationN/A