"Getting pregnant can be tricky. One way an aspiring mother can make it easier is to know when shes most fertile a period spanning a few days every month when her body undergoes hormonal changes. And certain bodytracking wristbands may be able to detect these subtle shifts in your biometrics like your heart rate and body temperature. Depending on the device it could even help you go one step further and actually conceive. Recently the womens health data startup Clue ran an internal test to see if Fitbits could improve the experience of women who track their periods on its popular app and are trying to get pregnant. Scientists put Fitbits on five employees and found that the devices could track their resting heart rate patterns during their menstrual cycles http The devices also showed that resting heart rate spiked shortly before ovulation began according to the Berlin company which presented data from the small preliminary study at the European Society of Human Reproduction and Embryologys annual meeting this month. Its a cheaper method for people who do want to get pregnant.  The advantage of a passive sensor is these things are done kind of autonomously so you dont need to do much except check when the resting heart rate starts coming up Clues head of scientific research Dr. Vedrana Hgqvist Tabor told BuzzFeed News. Its a cheaper method for people who do want to get pregnant. Fitbits arent the only wearables that can track fertilityrelated biometrics in the background. After a Kickstarter campaign YONO just started shipping an earpiece http designed to track your body temperature at rest. And Ava http is working on a smart wristband that aims to help women conceive.  How an Activity Tracker Caught an Unexpected Pregnancy Fitness trackers by nature of being worn around the clock have the potential to capture unexpected insights about how your body works  and simplify laborious acts like manually figuring out httpamericanpregnancy.orgpreventingpregnancynaturalfamilyplanning your fertile days. That traditionally involves taking your temperature when your body is at rest http examining your cervical mucus and recording this data every single day on a calendar. Clues study which ran for  months beginning in April  didnt set out to see whether the Fitbit ChargeHR could identify when a woman becomes pregnant. Rather it was exploring whether the device could reliably track an alreadyknown occurrence http how a womans resting heart rate changes when shes experiencing rising hormonal levels linked to ovulation. For the experiment five women under  wore a Fitbit ChargeHR to bed. Thats because resting heart rate data can be captured at its purest when a person is asleep and not moving. The women also logged their periods on Clues app and took daily urine tests to track when there was a surge in the key hormones that signaled they were entering ovulation. Researchers were watching all these biometrics as the study participants went through their cycles. A womans fertile window  when shes likeliest to get pregnant  usually occurs two weeks after the start of her last period and lasts for about six or seven days ending on the day of ovulation. As the researchers had hypothesized the participants Fitbits captured a portion of this fertile window by showing that their resting heart rates rose one or two days before ovulation as well as during ovulation itself. So a woman who saw a bump in her resting heart rate history could use that information to schedule intercourse with her partner Hgqvist Tabor said. And the study had one particularly unexpected outcome. Clues marketing director who was participating was puzzled when her Fitbit said her heart rate was up by several beats per minute. Hgqvist Tabor said she soon realized what the finding meant and broke the news to the marketing director She was pregnant. The happy discovery was similar to one earlier this year when a man posted on Reddit about how his wifes Fitbit showed an uptick in her resting heart rate. Upon a Redditors suggestion she took a test that confirmed she was in fact pregnant. An expert told BuzzFeed News https_term.kiKmZLkLQ at the time that her heart rate increase may have been an indirect result of elevated body temperature another symptom of pregnancy. But Dont Think Of This As Birth Control Even though Clues marketing director happened to find out she was pregnant from her Fitbit the point of the study was to demonstrate that its possible to use Fitbit as a conception tool not as a pregnancy test Hgqvist Tabor said. And thats provided that a couple doesnt have any other fertilityrelated problems. Manually figuring out your fertile days is a laborious multistep process you have to do every single day.  However Hgqvist Tabor said this information by itself should not be used as a birth control method. A woman will be fertile four to five days before her increased resting heart rate will start showing up on a Fitbit  so having unprotected intercourse during this period could in fact lead to an unintended pregnancy. If youre curious exactly what kind of increase in resting heart rate you should look out for Clue hasnt revealed that information yet but says it will publish that and other data in a paper later. Hgqvist Tabor says its tricky because it depends on the individual and can range from a few beats per minute to  beats per minute. One reason to potentially shy away from trusting Fitbits heartrate sensors In a classaction lawsuit http some unhappy consumers have accused them of being inaccurate. Regardless Clue scientists say that they were more interested in the devices ability to capture the daytoday differences in someones resting heart rate which seemed to be consistent and less interested in whether the devices could produce the exact values of resting heart rate. You will get a relative change even though it might not be as accurate as a chest strap said Clue cofounder Mike LaVigne. And while resting heart rate can be a telltale sign of ovulation Lea von Bidder CEO of Ava says consumers shouldnt rely on that measurement alone if theyre serious about getting pregnant. Her companys wristband is designed to track eight physiological markers in addition to heart rate variability including skin temperature pulse rate breathing rate and sleep. The Ava bracelet will launch this summer. As a lowrisk medical device registered with the Food and Drug Administration it doesnt need indepth review by the agency to be sold according to the company. By monitoring these multiple biomarkers while a woman is asleep Avas wearable and app can notify her during the five days shes most fertile ending in ovulation according to von Bidder who says Ava has conducted studies on about  people. Von Bidder said it was promising to see that Fitbit might be able to provide heart rate data to women trying to conceive. But we also know that heart rate alone will not be enough she said. Wearables have a wellworn reputation as stepcounting machines. But as Clues and Avas fertility research indicates increasingly sophisticated sensors and algorithms could significantly open up wearables capabilities  and make them that much more able to tackle bigger complicated health issues."