How to detect ovulation?
There are a few different types of ovulation trackers out there, and they each work differently. Some apps and devices rely on one metric alone to predict and track ovulation, while others use a combination. The main types are below.
It’s worth noting that when you compare all the possible measures for predicting and tracking ovulation, BBT and urine hormones are the most well-studied and well-accepted, according to Belinda Coker, MRCGP, MBBS, DRCOG, DFFP, an obstetrics and gynecology- trained GP, and founder of Your Trusted Squad, a concierge service for fertility and IVF.
Of the two, urine hormones are considered the most reliable and accurate, adds Aaron Styer, MD, a reproductive endocrinologist, OB-GYN, and founding partner and co-medical director of fertility and IVR clinic CCRM Boston.
Basal Body Temperature (BBT): Since body temperature rises 0.5 to 1.0°F after ovulation, taking your temperature daily can help you estimate your ovulation period. If you take your temperature orally, it should be done right after you wake up (ideally after you’ve slept for at least 4 hours), so some of the wearable fertility trackers make this process easier. Your BBT can also be measured vaginally (commonly called core body temperature) or via your skin at certain parts of your body, such as your armpit.
However, this method cannot predict the window of ovulation ahead of time, as temperature changes are usually only detected after ovulation, Dr. Styer said. This means that when using temperature alone, it takes several months of data to accurately predict ovulation, according to Dr. Steer – and that’s only if your cycles are consistent.
Most trackers and apps that rely on BBT have a proprietary algorithm that helps predict your ovulation dates, but many also measure or ask for additional inputs for more accurate predictions, such as ovulation test kit results.
Urine hormones: Various hormones rise and fall around ovulation, and some ovulation trackers measure their presence in your urine to make a prediction. The most commonly measured hormone is luteinizing hormone (LH). “The Pituitary Gland [a gland in the brain] will release LH into the bloodstream to signal the ovary to release an egg,” explained Dr. Styer. “This hormone release is called the ‘LH surge’ and usually occurs about 24-48 hours before ovulation. “LH can be detected in your urine, which is what these devices test for.
As tracking devices become more advanced, some of them have also begun to measure other hormones involved in the ovulation process, such as estrogen and follicle-stimulating hormone (FSH).
Algorithms: Some apps and trackers use proprietary algorithms to predict your ovulation window. If you use an app, you need at least one additional data point besides the algorithm, such as BBT or urine hormones, to accurately predict and track ovulation, Dr. Coker said. This is because algorithms are based on the average cycle in research (or across the app or device’s user base), and many people have longer or shorter cycles than the average.
Other metrics: Some tracking devices use measures that are less well recognized, such as pulse, breathing rate and cervical mucus. It’s very exciting to see new types of data being used to track ovulation, Coker said, but it’s important to know these metrics aren’t as scientifically validated as BBT and urine hormones.