If you’re trying to get pregnant, a handy skill you’ll want to nail down is the ability to figure out when you’re ovulating. That’s when an egg is released and can be fertilized by sperm—and it only happens once per cycle.
What is ovulation?
Ovulation happens when one of the ovaries releases an egg that’s ready to be fertilized. In the lead-up to the big event, a group of follicles (little sacs that hold the eggs) in your ovaries start to grow after the first few days of your period. Your hormones help this process along, and one of these follicles will respond better than the others and stand out as the dominant follicle.
Inside this dominant follicle, there’s a single egg and its support system, including granulosa cells. As the dominant follicle grows, more granulosa cells replicate and they produce estrogen (which has the important job of thickening the endometrium to prep for an embryo to implant later on). When estrogen levels rise past a certain threshold for a long enough time, it cues a spike of luteinizing hormone (LH). That LH surge triggers ovulation: within 12 to 36 hours, the dominant follicle bursts open and releases the egg from the ovary. Along with this important step, the LH surge also transitions the immature egg into a mature egg (a process called meiosis) and releases it from the walls of the follicle so that it can make its way outside the ovary.
That egg can now travel to the fallopian tube. If there are sperm around, this is where fertilization goes down. If the egg is fertilized by a sperm cell, that early embryo (which rapidly divides from a single cell, to two cells, and into hundreds within five to six days) travels down to the uterus, then hatches from its shell to find a good landing spot within the endometrial cavity. Meanwhile, the follicle shell that was left behind (now called the corpus luteum) starts producing progesterone to support a thick and cushy uterine lining. If an embryo implants, it releases a hormone called hCG (the pregnancy hormone—the same one that blood or urine tests measure for). The hCG stimulates the corpus luteum, so it will continue releasing progesterone to keep that lining plush and support the early growth of the placenta.
On the other hand, if the egg doesn’t become fertilized within 24 hours, it breaks down. Without the chain of events to release hCG and keep the corpus luteum alive, it only lasts for about two weeks and your progesterone level starts to fall. That drop tells your body to shed the uterine lining it had been building, so it can start fresh next cycle. Enter, your period.
When does ovulation occur?
Ovulation takes place once per cycle. In the average 28-day cycle, ovulation happens around day 14 (start counting from day 1, the first day of period bleeding). But not everyone has a 28-day cycle, so it’s possible to have normal healthy ovulation sooner or later. The pre-ovulation (first) part of each person's cycle can vary, but the luteal phase (the part after ovulation) is rather consistent at two weeks (the time it takes for the corpus luteum to dissolve if the pregnancy hormone hCG isn’t keeping it going). So if you regularly have 35-day cycles, you likely ovulate around day 21 (35 minus 14 equals 21 days). And while this calendar method is a good starting point, read on for other ways you can more closely track ovulation.
What are the signs and symptoms of ovulation?
If you’re trying to get pregnant, you’ll want to be able to pinpoint the timing of your ovulation so that you know the best days to have sex or inseminate so that the sperm is ready to meet your egg (hot tip: sperm can live in the fallopian tubes for a few days, whereas an egg only lasts for about a day if it isn’t fertilized, so you’ll want the swimmers ready and waiting—not the other way around).
Even if you’re not actively trying to conceive, understanding if and when you ovulate can give you a better picture of your fertility and general health. There are a few different ovulation signs and symptoms you can look out for:
Vaginal discharge and mucus change throughout your cycle, and you can look for specific characteristics just before ovulation.
After your period stops, it’s common to have wet, creamy and/or thin discharge. During this part of your cycle, your likelihood of pregnancy is low. Shortly after this though, you may notice that your discharge is now thicker, clear and slippery—sort of like the appearance of egg whites. It also can stretch! If you hold a small amount between your finger and thumb, then pull them apart slowly, your cervical mucus should stretch about an inch or so.
This egg-white cervical mucus shows up a few days before you’re set to ovulate. The jelly-like fluid represents the rise in estrogen before your LH surge, and thus, your fertile days. Although an egg only lives for about a day after it’s released, sperm cells can survive for up to five or six, and that’s thanks to this cervical mucus (and good quality sperm, of course!) which protects sperm from the vagina’s acidity so they can survive longer.
To keep an eye on changes to your cervical mucus, check toilet paper, your underwear or with a gentle sweep of a clean finger.
Basal body temperature (BBT)
While cervical mucus can signal that you’re about to ovulate, changes to your basal, or waking, body temperature happen right after. Your BBT rises in relation to your progesterone levels, which increase post-ovulation and during the luteal phase (from ovulation to the day before your next menstrual period). So, you can look for a rise and plateau of your temperature to know when ovulation has occurred.
Since BBT is a waking temperature, you’ll need to measure it first thing in the morning, before you get out of bed or start moving around. It’s ideal to take your temp at the same time every day, and you’ll need a precise thermometer that can measure to at least one decimal (one-tenth of a degree).
Keep in mind that your BBT can easily vary from day to day by 0.2 to 0.4 degrees Celsius. What you’re trying to catch is a jump in temperature by more than this. That jump corresponds to rising progesterone levels, indicating that ovulation has happened likely within the last day. (Whereas cervical mucus can signal the ovulation is going to happen and help you plan, the BBT is less helpful on this front because the rise happens after ovulation.)
The best way to see this is by graphing it out. Many cycle-tracking apps will do this for you, or you can do it yourself with a spreadsheet or the old-school method of pencil and paper.
BBT is less accurate when you don’t get enough consecutive of sleep before waking or if you get up and walk around before taking your temperature. Having a thyroid condition or drinking alcohol the night before can both affect BBT as well.
Though tracking BBT isn’t 100-percent accurate for ovulation or rises in progesterone, it can help you identify patterns in your cycles and specifically when ovulation typically happens so you can predict it for your next cycle and time intercourse/insemination accordingly.
Ovulation pain (“Mittelschmerz”)
Some people can physically feel when they’re ovulating. You might notice a twinge, minor cramping, dull pain, fullness or pressure around your lower abdomen and specifically around the ovaries (find your front hip bones and move your fingers towards each other and down a few inches).
“Mittelschmerz pain” translates to “middle-pain”: discomfort in the middle of the cycle, when you ovulate. It’s experienced by about 20 percent of people who ovulate and can change from cycle to cycle. The theory is that it coincides with the rupture of the dominant follicle as it releases the egg. After all, the dominant follicle gets to roughly two centimeters when it’s ready for ovulation.
Other theories about the cause of Mittelschmerz suggest it’s the physical pressure of the follicle itself and the muscle contractions that occur after your LH surges.
Your libido, or feelings of sexual arousal, can go up and down with the changes in your hormones throughout your cycle. Some people who ovulate find their sex drive is highest pre-menstruation and just before or around mid-cycle. This finding isn’t consistent, so don’t be discouraged if you don’t find yourself feeling frisky around your period or before/during ovulation.
If you’re feeling in the mood and also notice that slippery, lubricating cervical mucus, you’re likely in your fertile window and this is a prime time for baby-making intercourse or insemination.
Another way to track ovulation is to use at-home ovulation tests (sometimes called ovulation predictor kits or OPKs). These are little strips that react with the hormones in your urine to predict when you’re about to ovulate. Specifically, they show when your LH (luteinizing hormone) surges, which sets off ovulation.
These tests are easy to do (just pee in a container, dip the strip and wait five minutes) and can provide clarity if you’re finding physical symptoms are tricky to nail down. Or better yet, try a combo approach of test strips and looking for the physical changes described above. To learn more about ovulation and at-home testing, check out our ovulation testing guide.