Traditionally, basal body temperature (BBT) was one of the only ways for women to confirm ovulation without a trip (or multiple trips) to the doctor’s office. The downside? BBT is notoriously difficult to monitor because you need to follow some pretty strict guidelines to get accurate data. Fortunately, BBT isn’t your only option anymore.
Recently, continuous core body temperature (CCBT) tracking has emerged as an easier and more accurate way to predict ovulation and pinpoint your fertile window. Read on to learn how ovulation affects your temperature and what BBT and CCBT can tell you about your fertility.
How are basal body temperature and continuous core body temperature related to ovulation?
Basal body temperature is your temperature when your body is fully at rest. For decades, women have used it as a tool to both try for and try to avoid pregnancy. There can be a bit of a learning curve to interpreting your BBT data, but the method itself is a relatively inexpensive, risk-free way to determine if and when you ovulate each cycle (1, 2).
BBT is defined as the lowest natural body temperature recorded after a period of rest (1). It’s natural for your body temperature to fluctuate throughout the day, but it will typically return to the same range each morning after a night of sleep. If you’re not ovulating, your BBT will probably stay within the same range all the time. However, if you’re ovulating, you may notice 2 distinct temperature phases during each menstrual cycle (2). This is called a biphasic chart.
Continuous core body temperature (CCBT), on the other hand, is measuring your body’s internal temperature 24/7. Hormones can change your temperature and these hormonal fluctuations can be detected with a CCBT sensor, such as the Priya Fertility System’s. By capturing CCBT, hormonal patterns can be detected and used to predict and confirm ovulation (3).
When you ovulate, a follicle in one of your ovaries releases a mature egg. Once the egg has been released, the now-empty follicle (called the corpus luteum) starts producing progesterone to help prepare your body for a potential pregnancy (1). This increase in progesterone causes a small spike in your temperature — about 0.5–1 degrees Fahrenheit. Your temperature and progesterone levels remain raised until the end of the cycle (4).
If you don’t get pregnant, your temperature, as a result of a drop in progesterone, will fall back to pre-ovulation levels around the time you get your period (1). If you do become pregnant, your BBT will remain raised for at least 18 days after ovulation (5).
Should you track BBT to confirm ovulation?
Tracking your BBT may seem like a simple task, but it’s a commitment that takes dedication and consistency. To start recording your BBT, you’ll need to buy a basal body temperature thermometer. You should be able to find a relatively inexpensive one at the drugstore or online. Keep the thermometer right next to your bed so you can take your temperature each morning immediately after you wake up (6).
Note: It’s important that you take your temperature before you do anything else in the morning. Even small actions like checking your phone, getting a drink of water, or talking to your partner can affect your BBT readings and make it harder to confirm ovulation (6).
To get the most accurate results, you’ll need to check your temperature at the same time and in the same way every day (6). Then, record the temperature on a chart. You can find printable BBT chart templates online or use an app like Kindara to chart your data. After a few cycles, you may start to recognize the biphasic pattern that we discussed above. That temperature shift that you see each cycle confirms that you ovulated.
Unfortunately, many factors can affect your BBT readings and make it harder to tell when or if you ovulated. This can include smoking, drinking alcohol, illness, stress, changes to your sleep schedule, shift work, and using an electric blanket (2, 6). On the other hand, these environmental factors don’t affect CCBT or its ability to predict ovulation (3).
If you think BBT tracking may not fit with your lifestyle, you have other options. The Priya Fertility System uses an intravaginal sensor and mobile app to measure continuous core body temperature (CCBT) and detect the subtle temperature patterns that occur 2-4 days before ovulation. You can use this data to plan when you have sex and maximize your chances of getting pregnant.
Are there other signs that can confirm ovulation?
A rise in BBT isn’t the only clue that your body gives you when you ovulate, but it is one of a few ways to confirm ovulation at home. CCBT, along with Priya’s dynamic algorithm, is another one. Your other fertility signs may not confirm ovulation, but they can still help you figure out when you’re most fertile (aka when you should have sex if you want to get pregnant).
Your cervical mucus (CM) plays a significant role in your fertility. As you approach ovulation and your estrogen levels rise, CM increases in volume and water content. This kind of CM helps make your vagina a protective place for sperm as they travel towards the egg (5, 7). After ovulation, your CM will start drying out again as your estrogen levels drop and progesterone levels increase (5).
Your cervical position can also give you some insight as to where you are in your cycle. Your cervix sits in the lower part of your uterus and connects to the upper part of your vagina. It has a small opening, called the os, that changes throughout your menstrual cycle (8). At the beginning of your cycle, the os will sit lower in your vagina. It will feel closed and firm to the touch. As you approach ovulation, the os rises higher in your vagina, gets softer, and starts opening up to allow sperm through (5).
Lastly, you can use ovulation predictor kits (OPKs) to detect the surge in luteinizing hormone (LH) that happens before ovulation. Like CM and cervical position, this LH surge cannot confirm that ovulation is actually happening, but it does let you know when your body is preparing to ovulate. OPKs typically detect an LH surge about 12–24 hours before ovulation (9).
How can a doctor confirm ovulation?
Your doctor has a few more tools at their disposal that they can use to figure out whether you’re ovulating or not. For example, they may perform a blood test about a week before your expected period to check your progesterone levels. Elevated progesterone is typically a good indicator that you’ve ovulated (10).
Less commonly, an ultrasound can be used to confirm ovulation. During this procedure, your doctor may perform either a transvaginal or abdominal ultrasound to observe the follicles in your ovaries. Before ovulation, one of the follicles will be thin-walled and filled with fluid. After ovulation, the follicle will rapidly and significantly decrease in size or even disappear (10, 11).
If you’ve been tracking your temperature, your healthcare practitioner can also take a look at your charts and help you interpret them. The temperature change that happens after ovulation is small, and it may be hard to recognize on your own. Your doctor may be able to help point it out on your chart so that you know how to confirm ovulation in the future.
BBT tracking can be difficult, but it’s a valuable tool for confirming ovulation when you’re trying to conceive. However, it’s not for everyone. If you find the idea of BBT tracking stressful or inconvenient — or you prefer an option that helps you predict your fertile window and confirms you have indeed ovulated — try CCBT tracking with the Priya Fertility System.
Catherine Poslusny is a writer and content marketing strategist based out of Norman, Oklahoma. She's written for healthcare companies since 2016, and she's most passionate about her work in women’s health, fertility, and reproductive rights. You can find her at catherinerosewrites.com.