Wearable device tracks infant milk intake during breastfeeding

A compact, unobtrusive wearable device can accurately measure expressed milk volume during breastfeeding in real time for better infant care.

Developed by a team of researchers from the US and South Korea, the device is a tiny module that collects data from four electrodes placed on the breast. Two electrodes deliver a low-level, safe electrical current through the breast tissue, while the other two quantifies the voltage difference associated with the passage of that current.

When breastfeeding, the amount of milk in the breast decreases, leading to a change in the breast tissue’s electrical properties, the researchers explained. The change, which is captured by the device, is directly proportional to the amount of milk removed from the breast, they added.

“This is a concept called bioimpedance, and it’s commonly used to measure body fat,” said Prof John Rogers from the Northwestern University in Evanston, Illinois, US, who led the device development.

“Because muscle, fat, bone, and tissues conduct electricity differently, bioimpedance can yield an accurate measurement of fat content. In a conceptually similar way, we can quantify the change in milk volume within the breast. This was the last strategy we tried, unfortunately. But fortunately, we found that we were able to make it work really well,” Rogers explained.

The data collected using the device are transmitted wirelessly via Bluetooth to a smartphone for real-time graphic display.

“The mother then can just watch on her phone [to see] how much milk is passing from her breast to her baby. It’s quite a simple device to use and to interact with,” Rogers said.

Consistent, reliable measurements

The device prototype was tested on 12 breastfeeding mothers both in the home setting and in the neonatal intensive care unit (NICU). Multiple measurements were taken from the same mothers up to 17 weeks.

In the initial phase of testing, mothers wore the device while pumping. This approach allowed quantification of the precise volume of milk being expressed—a critical step for calibration and validation. In a separate testing session, Rogers and colleagues compared data collected from the device to the difference in the weight of the baby before and after breastfeeding.

Overall, the results of the testing demonstrated the practical utility of the wearable device. Notably, the measurements taken by the device showed striking agreement with the amounts of milk pumped into a bottle. [Nat Biomed Eng 2025;doi:10.1038/s41551-025-01393-w]

Better NICU care

The device was developed to provide reassurance and valuable information to mothers. It would allow mothers to determine the precise amount of milk their babies are consuming during each nursing session. But the researchers saw that the device would particularly benefit infants in the NICU who have specific nutritional requirements.

“For babies who are born prematurely or who are recovering from a surgery, they can only eat small amounts of milk very slowly. Oftentimes, we cannot allow them to breastfeed because there’s no way for us to know how much milk they are getting from mom,” said one of the researchers Dr Jennifer Wicks from the Northwestern University. “Having a sensor to monitor this would enable these babies to breastfeed more successfully with their mom.”

Wicks also noted that some premature infants may have underdeveloped digestive systems, which make them more susceptible to feeding intolerance. Knowing exactly how much milk they are consuming is crucial in minimizing the risks of developing intestinal disorders and reflux, she pointed out.