Kegg Fertility Review

Fertility tracking is one of the most important things a woman can do for her health. Apart from its importance in planning or avoiding a pregnancy, it's also instrumental in establishing what's normal during your unique menstrual cycle. After all, to be an active participant in your healthcare, you need to be familiar with how your body works.

In the last decade or so, we've seen the rise of fertility-awareness methods that use smart devices to analyze biological data — and kegg is one of them. Launched in 2020 by Lady Technologies, kegg leverages electrical impedance spectroscopy (EIS) technology to measure the hormone levels in your cervical fluid, predict your ovulation window, and relay key biomarker information to a mobile application.1 Plus, the device doubles as a Kegel ball.

In this review, we examine the science behind kegg's sophisticated approach to fertility awareness and see how this fertility tracker measures up to the competition.

The kegg fertility tracker is an FDA-registered Class I medical device that provides accurate fertility interpretations with just two minutes of use per day, along with a solid safety pedigree and significant privacy protections for the user. The $259 up-front cost is high, but unlike many of its competitors, it doesn't require you to purchase regular refills or add-ons that would inflate the base price. The intravaginal use method may be uncomfortable for some, and the results may not be as consistently accurate as a urine test, but the kegg fertility system is, overall, a viable fertility-awareness method for women who want to conceive, avoid pregnancy, or familiarize themselves with their unique cycles.

Over the past two decades, Innerbody Research has helped tens of millions of readers make more informed decisions involving staying healthy and living healthier lifestyles.

This review of the kegg fertility monitor centers on the research surrounding electrical impedance technology and the reliability of analyzing cervical mucus to predict ovulation windows. In total, we pored over more than two dozen factual sources, including scientific studies and reviews, to determine whether kegg and its foundational premise held up to scrutiny. As usual, we also submitted ourselves as subjects of the customer experience, which entailed ordering the kegg tracker and acquainting ourselves with its functions.

Additionally, like all health-related content on this website, this review was thoroughly vetted by one or more members of our Medical Review Board for accuracy.

Whether you're looking to get pregnant, keep from getting pregnant, or become more familiar with your menstrual cycle, you'll want a fertility tracker that delivers precise results through an approachable means without compromising your data. That's why accuracy, privacy, and convenience were our foremost considerations when assessing the kegg system.

At the same time, you don't want to break the bank or put yourself in harm's way, which is why cost and safety rounded out our evaluative criteria.

Here, we break down how we rated kegg in each category.

Accuracy

Based on our research, the electrical impedance technology that drives the kegg fertility tracker is quite accurate, though not quite as bulletproof as urine testing.

As you near your fertile period, your cervical mucus undergoes both physical and compositional changes. It takes on a thinner, stretchier consistency that alters an electrical impedance reading (i.e., a measure of the resistance or opposition to an electrical current) to signal a shift in your cycle,2 while an increase in electrolytes and hormones indicates biological changes associated with peak fertility.3 4 These are the markers the kegg electrodes detect, and according to two studies (self-funded but with sound methods), they're sufficient for predicting impending ovulation.

One of the studies compared kegg's performance to urine testing and found that the kegg device could predict ovulation with 63.6% sensitivity (true positives) and 81.8% specificity (true negatives).5 If we compare the findings to those of a separate study (one not funded by the company), we see that kegg appears to be superior to urine testing when it comes to identifying true negatives, but urine testing is better at identifying true positives.6

The other self-funded study examined how kegg fared against basal temperature monitoring, and the outcomes were entirely in kegg’s favor: kegg was found to be 7.14% more sensitive and 20.35% more specific.7

The takeaway here is that kegg seems to occupy the upper echelon of a middle ground with regard to accuracy. It's significantly more precise than using a basal body thermometer but less precise than urine testing for identifying a true positive. For comparison, studies from 2007 and 2021 suggest that competitors Clearblue and Mira, both urine-based fertility monitors, have the potential to increase pregnancy success by over 8%, which is considered statistically significant.26 27 Therefore, urine testing may be the better choice for women who are trying to conceive, but kegg may be preferable to those who want to avoid pregnancy or to better understand their cycles.

Privacy

Kegg is an app-connected system that monitors health data — reproductive health data, at that — and any system that sends personal information to the cloud leaves concerns about privacy.

Fortunately, kegg appears to do a solid job of protecting its users' anonymity. The company’s privacy policy states it will never share or sell user data to third parties, and session data is encrypted and anonymized before it's stored in kegg's servers.

There's also no requirement to verify personal identity during registration. Verification is done by scanning a QR code on the user manual. While you do have to provide a name and email address, you don't have to use your real name or main email account. In contrast, some fertility trackers, such as Tempdrop (an app-connected thermometer), reserve the right to validate your identity.

Altogether, kegg’s privacy policy is similar to competitor Mira’s, which also anonymizes fertility data, uses it for research purposes, and gives users the choice to opt out. You can learn more about Mira in our dedicated review.

A final privacy measure worth mentioning is packaging, as you may not want your neighbors to know what's in the box sitting on your doorstep. Your kegg order should arrive, as ours did, in a plain brown box with no obvious markings to betray its contents. The only giveaway is the name "Lady Technologies LLC" on the address label, which doesn't exactly announce that you have a fertility tracker in the box. We always appreciate such discreet packaging.

Convenience

Like other fertility tracking methods, the kegg device has some pros and cons when it comes to its convenience.

We'll start with the cons. The primary one is that it's designed to go inside a sensitive part of the body. Every day (save for days you're menstruating), you insert the device intravaginally and wait for two sets of vibrations — one to signal the start of your reading and two to signal the end. For some (if not many) people, intravaginal use could be uncomfortable, even painful, but there's no getting around it with the kegg system. The second con is that you have to remember to take your reading within the same two-hour window every test day; at least part of your daily schedule will have to revolve around it.

Now, let’s look at the pros. First, the readings are pretty fast: about two minutes from start to end. That minimizes not only the time you have to spend with a device inside your body but also how long you have to wait for your results (in contrast, a urine test like Mira requires around 20 minutes of wait time before it churns out your data). Second, intravaginal use means you don't have to deal with urine, which is a big upside for a lot of people. And third, the device is small enough (about the width of 1.5 tampons) that many users shouldn’t experience serious discomfort.

If you’d prefer a more convenient method of fertility awareness than either kegg or a urine test, then the basal temperature method is probably your best alternative. But the issue there is that you’d be trading accuracy for ease of use, which we discuss in greater detail in later sections.

Cost

An 8.7 cost rating for a $259 device? We understand we have some explaining to do. Indeed, $259 isn't anything to scoff at, but cost value is a relative concept, and you have to look at the alternatives to see where kegg stands in the competitive landscape.

The fertility-tracking device market tends toward the high end of the price spectrum. Many of the top kegg competitors we've identified are roughly comparable in price even at their base levels (e.g., $239-$309 for Ava Fertility, $239.25 for Daysy, and $219 for Tempdrop 2.0). Then you have to account for their ongoing expenses.

You see, kegg is a one-time-only purchase — no ongoing expenses. You don't have to pay for urine stick refills or the premium version of the app, so the cost you pay up front is the same cost you'll have ended up paying after a year's use.

In contrast, four out of our six alternatives require that you continue paying the company if you want to get the best use out of your product. Take Clearblue, for example. At $91.18, it's the least expensive product we discuss in our review, but you also need to purchase regular refills of urine sticks if you want to continue tracking your fertility. The original purchase comes with 30 sticks, but refills cost $55.70 each. In five months' time, you'll have spent upwards of $300 using Clearblue. (With Inito and Mira, the other urine tests we discuss, you’ll surpass kegg’s price point in even less time.)

Consider Tempdrop, too, one of the thermometer alternatives we mention later on. To access the features you'd likely want in a fertility tracker (fertility insights and data interpretation), you'd have to pay an ongoing $4.49 monthly subscription or $35.99 up front for the year. So, by the end of the year, you're potentially looking at an overall cost that will have exceeded kegg’s.

On top of the long-term cost value, kegg has a kicker for customers who are trying to conceive: If you don't get pregnant within a year of consistent use, you can request a full refund. Only one of the competitors on our list, Ava Fertility, offers a similar guarantee.

Safety

The kegg fertility tracker requires intravaginal use, but its safety pedigree should relieve at least some of the concerns you may have with inserting an electronic device inside your body.

The kegg tracker happens to be an FDA-registered Class I medical device, which means it presents only "minimal potential for harm to the user."8 It's an FCC-registered device, too (indicating that it satisfies regulatory criteria for wireless devices), and has passed IEC 60601-1-2 medical device EMC testing (i.e., its radio frequency emissions are within a safe range).9

What would have boosted kegg in our safety evaluation is FDA clearance, which indicates a device is substantially similar to an existing device that has been approved by the FDA.30 Kegg seems to lack clearance, unlike competitor Ava.

Kegg is an FDA-registered intravaginal fertility-tracking device made by Lady Technologies, a company that specializes in tech-based women's health products. Per regulations, entities that produce or distribute medical devices intended for use in the United States must register with the FDA every year.10 A quick search on the FDA's registration database confirms that Lady Technologies is current on its registration status at the time of this writing. In other words, the company behind kegg is maintaining its regulatory compliance — the least we can expect from a responsible, accountable business entity.

The kegg fertility-tracking device consists of two main parts:

• The head: the egg-shaped portion that contains the sensor
• The tail: the slim, flexible portion that curls off the head like a candy cane

Apart from the gold-plated electrode cap and ring at the front end of the head, the device is entirely white with a soft matte texture. The head is about two inches long from front to base. At its broadest, it measures the width of approximately 1.5 regular-size tampons.

Other than the device itself, the box comes with a user manual, a cup-shaped charging base, a USB-A to USB-C charging cable, and a wall adapter. Charging the kegg tracker entails inserting the head of the device into the charging base.

Kegg is a two-in-one device, which is novel among its competitors (none of the other brands we discuss in this review serve dual purposes). Its primary function is to track fertility using a technology called impedance, which we discuss in the next section. Outside of menstruation days, you take a daily fertility reading and the sensor transmits the analysis to the connected mobile app. Secondarily, it's an optional Kegel ball. During your reading, you can choose to follow guided Kegel exercises through the app.

In case you were wondering, the name "kegg" is a pun. It refers to the device's egg shape, its primary function of tracking your ovulation, and its secondary function as a Kegel ball. Really, the whole product design has a pun-like playfulness: The head and tail together resemble a sperm cell curled into the fetal position. Maybe the resemblance is coincidental, but we think it’s something worth remarking upon.

The kegg device is part of a larger system that integrates advanced sensing technology, mobile app access, and optional strengthening exercises. Below, we discuss the specific role that each component plays in the kegg ecosystem.

Electrical impedance spectroscopy

The kegg tracking device relies on a technology called electrical impedance spectroscopy, often abbreviated as “EIS.” Unless you have a working familiarity with electrical engineering, impedance is a tough concept to understand, but we're going to simplify it as much as possible. Essentially, it's resistance to an electrical current. In medical applications, applying an alternating current at various frequencies through a medium can detect physical transformations that are otherwise unnoticeable by visual inspection. Thus, impedance is a useful tool for diagnosing cellular changes, such as those associated with cancer formation — or, say, ovulation, the most fertile phase of the menstrual cycle.11

Now, kegg works by analyzing the electrolyte levels in your cervical mucus. Here's how it all connects:

Kegg readings should be performed daily, except on days you’re menstruating, and ideally within the same two-hour window every day. To take a reading, you need to insert the head of the device intravaginally, with the tail oriented upward. A single vibration signals that your reading has begun, and two vibrations indicate that it's finished.

As you consistently take readings with your kegg fertility tracker, it records trends in your electrolyte makeup and transmits the data via Bluetooth to the connected mobile app. When your present electrolyte balance aligns with your ovulation-related trends, it signifies peak fertility. You can use that information to plan a pregnancy, avoid a pregnancy, or better familiarize yourself with your unique menstrual rhythms.

There is a supporting pilot study that directly validates kegg's ability to predict a user's fertile window. Mind, it's a self-funded study, which introduces the potential for bias, but it does offer useful data for evaluating efficacy. Also, it's important to acknowledge that a scientific study on the kegg device probably wouldn't exist if Lady Technologies hadn't provided the financial support to make it happen in the first place. That said, we also acknowledge that studies have been done on competitors like Mira and Ava without self-funding, and we do wish there were a kegg study without any direct ties to the manufacturer.27 29

Published in 2022, the study involved 11 women aged 18-44 with normal hormonal profiles who avoided hormonal contraceptives, intrauterine devices, and vaginal treatments for at least two months. All participants used the kegg tracker for two minutes every morning across three consecutive menstrual cycles, and hormonal activity was corroborated through urine samples, blood samples, and vaginal ultrasound. In the end, the researchers calculated that kegg had a sensitivity of 63.6% and a specificity of 81.8%.5 That is, on average, the kegg fertility tracker correctly identified true positives in 63.6% of cases and true negatives in 81.8%.

Based on the findings, we can say that kegg is a fairly accurate at-home diagnostic tool for fertility, but it's not the most accurate. For example, the findings of a 2017 review in Bioengineering & Translational Medicine suggest that urine analysis has the potential to yield a sensitivity of 100% — a much more accurate identification of true positives.6 But, as you'll see in the "Alternatives to kegg" section later on, urine tests can come with significant downsides.

The kegg mobile app

Like most of the competitors we discuss in this review, kegg has a mobile app (compatible with Android and iOS, and named "kegg" in either app store) through which you access your fertility data and related insights. But in contrast to competitor Tempdrop, you don't have to pay for a premium version to get the most out of your readings. You could say the kegg app is the premium version by default, with no data points hidden behind a paywall.

On your first startup, you'll have to scan a QR code or input the associated numerical code to complete registration. On the following screen, you’ll have the option to allow Lady Technologies to use your account for women’s reproductive health research (similar to competitors Ava and Mira), but you don’t have to opt in. Later in the registration process, kegg gives you the choice to calibrate your app for regular or irregular periods, which we think is a nice, inclusive gesture.

Once you're all set up, you access the main chart by the Cycle tab, found in the center of the bottom row of your app interface. The lion's share of the main chart is taken up by a line graph that conveys the history of your kegg readings. As a new user, you’ll see just one light-green line at first; this is your daily reading line. Then, as you take more readings, a dark green line called the trendline will appear. The trendline is a predictive data point calculated by kegg’s algorithm. So, even with a one-day rise in your daily reading line, kegg can detect whether it’s lower than normal and thus determine your likelihood of approaching your fertile window. In theory, then, the longer you use kegg, the more accurate the trendline becomes.

The lines correspond to conditions in the vaginal environment. A descending line means your cervical mucus is approaching a consistency associated with higher fertility, whereas an ascending line means you’re in a post-ovulation phase. If you find that to be counterintuitive, just remind yourself, “A line going down means pregnancy chances go up.”

As your estrogen levels rise and your body approaches ovulation, the line graph descends into what kegg terms the "fertile valley,” which denotes your window of highest fertility. Users with regular cycles normally have sharply delineated valleys, wherein the levels drop dramatically for several days before slowly climbing up to normal levels. On the other hand, irregular or long cycles may produce shallower valleys, sometimes multiple ones within a single cycle. If your goal is to get pregnant, engaging in intercourse during every dip in the line graph should offer the greatest odds of conception.

Below the graph are additional predictive data points that effectively summarize the graph and salient details about your cycle:

• Cycle day: where you currently are in your menstrual cycle
• Period in: how many days until your period should start
• Fertility: how fertile you are based on your current and historical readings (e.g., "Low" or "Likely")

Elsewhere in the app, you'll find a calendar view (one of those features often hidden behind a paywall, as with Tempdrop). The calendar allows you to keep detailed notes in a wide range of sex- and fertility-related areas, including, but not limited to, period bleeding, spotting, sex drive, body temperature, cervical mucus consistency, and urine testing. The calendar can be helpful not only for maintaining a record of key health markers but also for mentally calibrating kegg's findings to your unique physiology.

Kegel ball function

We mentioned earlier that kegg doubles as a Kegel ball, with guided exercises accessible through the mobile app. It's part of what differentiates kegg in the fertility-tracking market.

A Kegel ball is a small, weighted object used intravaginally to perform a series of contractions and relaxations (called Kegel exercises) that help strengthen the pelvic floor — the muscles that support the bladder, rectum, and uterus. Strengthening these muscles can enhance your control over waste functions (urination, bowel movements) and improve sexual pleasure. More relevantly to many kegg users, pelvic floor training may allow for an easier pregnancy and delivery, as it can help with:

Generally, yes, the kegg fertility tracker is safe to use. In fact, several designations validate its safety:

Women who want to become pregnant or those who want to avoid pregnancy can most directly benefit from using the kegg fertility tracker. It's also useful for women who want to be more knowledgeable about their reproductive health, as it can provide key insights into the biological changes associated with their menstrual cycle, the expected arrivals of their periods, and their average length of menses.

Women with regular menstrual cycles stand to realize the greatest advantage by using the kegg system, as a regular cycle is likely to produce the most easily interpretable data. An irregular cycle doesn't exclude you from use (the app even asks you to specify whether your cycle is regular or irregular), but your data may require additional scrutiny to determine whether you’re approaching ovulation.

However, the kegg system isn't ideal for all women. For example, those who aren't interested in monitoring their fertility or reproductive health would have little to no reason to invest in any fertility-tracking device. Also, for those with endometriosis or a pelvic health condition (e.g., vaginismus, an involuntary tightening of the vagina in response to insertion, which could cause pain when using the kegg device), kegg recommends consulting with a health provider to determine suitability.28

In addition, for certain populations, a different fertility-awareness method would be preferable. If you're primarily concerned with any of the following factors, you may want to consider a different approach:

Any app-based health product raises concerns about user privacy, with women's reproductive health being an especially sensitive matter. To kegg's credit, its app does a fair job of ensuring that whatever information you share with the company can't be traced to your identity. Below are some of the most salient points we've found in kegg's privacy policy:

• General anonymity: App registration doesn't necessarily require that you provide personally identifiable information. Though you do have to input a name and an email address, there's nothing stopping you from using throwaway alternatives. For example, we successfully registered our device with the name “Anonymous Bosch.”
• Third parties: The company states it will never share or sell your data to a third party. Third-party applications may have access to your kegg account, but you can revoke the access through your phone's settings.
• Encryption: Session data is sent to and stored in kegg's servers, but the data is encrypted and anonymized; it can't be used to identify you personally. Such encryption practices are fairly common among fertility trackers — for example, Ava also stores your data anonymously — though some may ask for evidence to verify your identity (e.g., Tempdrop).

Kegg's respect for customer privacy extends to its shipping, too. If your order is anything like ours — and there's no reason it won't be — it will arrive in a plain brown box completely unadorned of identifying emblems. The only detail that could possibly give away its contents is the sender's name ("Lady Technologies LLC") on the address label, but it's general enough that someone would have to know what the company does to surmise what the box contains.

Kegg's price tag is both a plus and a minus. Let us explain.

The kegg fertility tracker costs $259 as a direct purchase. It’s the same price on MyOvaterra but $10 more expensive ($269) on Amazon. That's a high up-front expense, no question, but it's also the only expense. You pay once for a fully integrated system that includes app access and all of the ancillary features. There are no add-ons or upgrades you need to purchase.

In contrast, most of kegg's competitors either require or strongly recommend an ongoing financial commitment, sometimes even for basic functionality. And your total expenditure can quickly escalate.

Take the Clearblue Fertility Monitor as an example. The monitor itself is one of the most cost-effective alternatives to kegg — only $91.18 on Amazon at the time of this writing — but a supply of 30 sticks is $55.70, and you’re expected to test up to 20 times per cycle. So, in just around five months with Clearblue, you'll have spent nearly as much as you would have on one kegg fertility tracker, and the cost only continues to rise the longer you stay with Clearblue.

Or you might consider Tempdrop, a wearable basal body thermometer (BBT). The basic model costs $149, while the advanced model is $219. Upon purchase, you get two months of the premium charting app, without which your access is largely limited to tracking temperature and symptoms. To keep the premium subscription, you have to pay $4.49 monthly or $35.99 up front for the year. Depending on which model and payment plan you select, the overall cost approaches kegg’s price point within 1-2 years.

So, indeed, kegg's up-front investment is higher compared to other trackers, but its all-inclusive functionality is actually more economical over the long term than others on the market. Also, it comes with a one-year warranty, and (as with many fertility-monitoring devices) it may be eligible for purchase or reimbursement through an FSA/HSA, though you’ll have to consult with your plan provider to confirm.

Checkout, shipping, and returns

On the kegg checkout screen, you'll notice quite a wide range of payment options, including three that allow installments:

• Credit card
• Venmo
• PayPal
• Google Pay
• Afterpay (option to pay in monthly installments)
• Shop Pay (option to pay in four installments)
• Affirm (option to pay in four or monthly installments)

It's a subtle enhancement of customer experience but one that many companies don't offer — and we appreciate the variety.

Standard shipping is free for orders to the contiguous United States or U.S. territories. If you complete your purchase before 1pm Pacific Time, your order will ship out on the same day. Kegg says to expect a four-day delivery window. Indeed, our order arrived on day four. As mentioned, apart from the sender's address, nothing on the box could possibly betray its contents.

Direct purchases don’t ship internationally. If you live outside of the United States, you’ll want to go through MyOvaterra, but even then, the shipping territories are limited.

Kegg's return policy is another case of upsides and downsides. On the downside, the money-back guarantee has only a 30-day return window from the purchase date, applies exclusively to sealed and unused items, and puts the responsibility for shipping costs on you, the customer.

On the upside, kegg touts a 12-month pregnancy guarantee that opens up a path to a full refund if you don't conceive within a year of purchase. Your eligibility for the refund hinges on whether you’re trying but have yet to conceive and if you meet the following criteria:

• You are at least 21 years old and within reproductive age
• You undergo menstrual cycles
• You are no less than six weeks postpartum and have undergone at least two menstrual cycles after the six-week postpartum period
• You have discontinued hormonal birth control for at least three months and have undergone two menstrual cycles since ending hormonal birth control
• You aren't lactating and have undergone at least two menstrual cycles since the end of lactation
• You are the original purchaser and bought your kegg tracker through the kegg website, Amazon, or MyOvaterra
• You consistently use the kegg tracker during the guarantee period
• You adhere to the directions for recommended use
• You permit kegg to review your app data to verify your eligibility

To take advantage of either the 30-day or the 12-month guarantee, use kegg's online portal to submit a return request.

There are a few reasons you might turn away from the kegg fertility tracker. It could be the up-front cost or the use method, or perhaps you need a more accurate solution better suited for an irregular menstrual cycle. In any case, maybe one of the following alternatives can provide what you're looking for:

Urine tests

Urine tests are at-home kits that usually measure luteinizing hormone (LH), which increases drastically about 1-1.5 days before ovulation.20 They work like pregnancy tests: You urinate on the end of a test stick or submerge the stick in a container of your urine for a specified amount of time. Some tests display the results on the stick itself via colored lines (also like a pregnancy test), while others require that you insert the stick into a digital or app-connected monitor for analysis. (All of the urine tests we recommend below are the latter variety.)

Earlier, we referenced a 2017 review in Bioengineering & Translational Medicine that stated urine tests yield the highest possible sensitivity at 100%. The same review also reports a 25% specificity — much lower than kegg's 81.8%.6 That means that using a urine test exposes you to a higher risk of false negatives, and that's no good for users who are trying to avoid pregnancy. Ironically, the low test specificity may be due largely to the high specificity of directions, as a deviation from strictly proper use can alter your results.

We mentioned, too, that you need to resupply yourself with testing sticks to continue using your chosen urine test. The cost adds up over time, and especially fast for ongoing users (i.e., those who are struggling to conceive or aren't aiming for pregnancy).

As long as you're okay with those downsides, you may be interested in one of these top-rated fertility urine tests:

Basal body thermometers (BBTs)

Ovulation raises basal body temperature, defined as one's lowest natural body temperature after a period of rest. As a StatPearls article on the subject explains, a woman who has begun ovulating experiences a "noticeable increase" in temperature ranging from 0.5 to 1 degree Fahrenheit compared to baseline, which is sustained until the start of menstruation.21 A BBT is a highly sensitive device, so it can accurately detect minute upticks in body heat. If you track your temperature throughout your menstrual cycle and then see an increase in the reading, that may be able to tell you, "Hey, you're within your fertile window."

For most people, the basal temperature method is probably easier than testing urine or using an intravaginal device like kegg. All you have to do is use the thermometer every day and record the number. You can insert it vaginally or rectally, but most people probably just place the thermometer under the tongue.

The thing is, temperature tracking isn't the most accurate fertility-awareness method. Optimal accuracy depends first on taking your temperature at the same time every day, preferably as soon as possible after waking; there's somewhat less leniency compared to the wider time frames allowed by the kegg tracker or urine tests. Second, your body temperature can fluctuate based on environmental, pathological, emotional, and behavioral factors. A bit of alcohol the night before, a bout of stress, or having a cold can all increase your temperature and throw off your readings.21

To put the matter in perspective, a 2024 study directly pitted BBTs against the kegg fertility tracker. Compared to a BBT, the kegg device demonstrated 7.14% more sensitivity, 20.35% more specificity, and 17.59% more total accuracy, suggesting a considerable degree of imprecision associated with the basal temperature method.7 Notably, this study, too, was funded by Lady Technologies, so we have to consider it with the same caveats we mentioned before, but the methods appear sound.

Given the imprecision of temperature tracking, it’s probably a viable option only for women who want to get pregnant and isn’t ideal for those who want to avoid pregnancy. For those who fall in the former camp and favor a simple approach to family planning, the following basal body thermometers may be of interest:

Natural fertility-awareness methods

Natural fertility-awareness methods involve no special gadgets and little to no monetary investment. Their reliability may vary depending on numerous factors, but the U.K.'s National Health Service reports they can be 75-99% effective for family planning.22

As long as you’re comfortable with the risk that attends human error, as well as the time and learning curve associated with each method, you may want to consider one or both of the following approaches: