No, her work was on determining the actual effectiveness of various stress reduction interventions on pregnant women:

“Physical Activity, Mindfulness Meditation, or Heart Rate Variability Biofeedback for Stress Reduction: A Randomized Controlled Trial”

I also misremembered, breathwork wasn't directly looked at as an intervention method, but I believe the HRV biofeedback did involve it to some degree.

https://link.springer.com/article/10.1007/s10484-015-9293-x