How to track 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 comparing all the possible metrics for predicting and detecting 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 fertility and IVF concierge service.
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’re taking your temperature orally, it needs to be done right after you wake up (ideally after sleeping for at least 4 hours), so some of the wearable fertility trackers make this process easier. Your BBT can also be measured vaginally (usually called core body temperature) or via your skin at certain parts of your body, such as your armpit.
This method can’t predict the window of ovulation ahead of time, though, since temperature changes aren’t usually detected until after ovulation, Dr. Styer said. That means when using temperature alone, it takes several months of data to accurately predict ovulation, according to Dr. Styer — 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 of these also measure or ask for additional input for more accurate predictions, such as ovulation test kit results.
Urine hormones: Several hormones rise and fall around ovulation, and some ovulation trackers measure the presence of these 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 in the bloodstream to signal the ovary to release an egg,” Dr. Styer explained. “This hormone release is called the ‘LH surge,’ and usually happens approximately 24-48 hours before ovulation.” LH can be detected in your urine, and that’s what these devices test for.
As tracking devices get more advanced, some of them have also started measuring 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’re using 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. That’s 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 metrics that are less well-recognized, such as pulse rate, 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.