Wearables might be able to screen for premature birth

Whoop’s new study shows changes in heart rate variability ahead of delivery. | Image: Whoop

Monitoring changes in heart rate in pregnant people may be a way to screen for people who will deliver prematurely, according to new data from researchers working at wearable company Whoop.

Preterm birth is risky and can lead to health complications for both the parent and the infant. But it’s hard to predict who might be likely to go into labor early. “Accessible, noninvasive screening options for premature birth can serve as early warning signs for pregnant people, giving them more time to find and administer interventions to improve health outcomes,” said Elizabeth Cherot, chief medical officer of the medical practice Axia Women’s Health, in a statement from Whoop.

The Whoop wearable device calculates users’ heart rate variability, or how often (and how much) their heart rate changes. Differences in variability can signal changes in the nervous system and can be a useful way to track shifts in the body. Higher variability is usually a sign that the body is doing well at adapting to different situations — it’s making changes to heart rate as needed. Lower variability is a signal that the body is becoming less adaptable. It’s also associated with a higher overall heart rate.

In April, a team of researchers published data on the heart rate variability of 18 pregnant women collected on the Whoop. They found that heart rate variability tended to get lower up until around 33 weeks of pregnancy (seven weeks before delivery) and then started increasing up through delivery.

The new study, which has not been peer-reviewed and is available as a preprint, built on that finding. The Whoop team looked at the heart rate variability of 241 pregnant users, 21 of whom had preterm births. For both people with preterm and full-term births, variability started to trend upward at around seven weeks until delivery. That inflection point, then, could be a signal of when someone is going to deliver — and if it hits early, then it could be a signal that someone might deliver early, the study authors said.

The findings are a promising first look at a potential big-picture trend in people who might deliver early, says Ben Smarr, a data scientist at the University of California, San Diego who does research on wearable devices and health. They don’t give information that can be used for individuals yet, though — a point the study authors also make in their analysis.

But this finding “tells me that there’s a relationship there that I should care about, and that digging into this in the future might bear some fruit,” Smarr says.

Whoop says it’s already using the results to make changes on the Pregnancy Coaching feature on this device. It’s adding week-over-week heart rate variability changes to the information it presents in weekly assessments, according to a statement. It will not be providing medical advice or mentioning premature birth, Emily Capodilupo, senior vice president of data science and research, said in an emailed statement to The Verge.

Smarr also does research on pregnancy and wearables (he’s done studies with smart ring company Oura) and says it’s good to see companies supporting research in this space. There’s very little understanding of pregnancy generally, and collecting data on how the body changes through noninvasive tools like wearables could improve health during that period.

“I hope it encourages other groups to realize that this kind of research is possible and that they could be contributing,” Smarr says.