When a woman is ovulating, her ovary is releasing a mature egg that can be fertilized by sperm. This happens once per menstrual cycle, typically about 14 days before the next period starts, and it marks the brief window when pregnancy is possible. The egg survives for less than 24 hours after release, which is why the timing matters so much for both conceiving and avoiding pregnancy.
What Happens Inside the Body
Ovulation is the climax of a process that starts days earlier. At the beginning of each cycle, several fluid-filled sacs called follicles begin growing on the ovaries, each containing an immature egg. Usually one follicle outpaces the rest and becomes dominant. As it grows, it produces rising levels of estrogen, which signals the brain that the egg is ready.
That estrogen spike triggers a sudden surge of luteinizing hormone (LH). Ovulation follows about 36 to 40 hours after this LH surge begins. The follicle wall breaks down through a cascade of enzyme activity that dissolves the tissue holding the egg in place, and the egg is released into the fallopian tube, where it can meet sperm. Blood or fluid from the ruptured follicle sometimes irritates the abdominal lining, which is why some women feel a twinge of pain on one side during ovulation.
The Fertile Window
Because the egg only lives for less than 24 hours after release, the window for fertilization is short. But the fertile window is actually wider than that single day, because sperm can survive inside the cervix, uterus, and fallopian tubes for three to five days. This means sex in the days leading up to ovulation, not just the day of, can result in pregnancy. In practical terms, the fertile window spans roughly six days: the five days before ovulation plus the day of ovulation itself.
For couples trying to conceive, timing sex within this window is the single most important factor they can control. For those trying to avoid pregnancy, understanding the fertile window helps explain why cycle-based methods require careful tracking.
Signs Your Body Is Ovulating
Your body gives several signals around ovulation, though not all women notice them equally.
Cervical mucus changes. This is one of the most reliable signs you can observe without any tools. In the days leading up to ovulation, rising estrogen transforms cervical mucus from thick and pasty to wet, slippery, and stretchy, often compared to raw egg whites. This consistency lasts about three to four days and serves a biological purpose: thin, wet mucus makes it much easier for sperm to swim through the cervix and reach the egg. Once ovulation passes, the mucus typically dries up or becomes sticky again.
Ovulation pain. Some women feel a dull ache or sharp twinge on one side of the lower abdomen, known as mittelschmerz. The pain likely comes from the follicle stretching the ovary’s surface before it ruptures, or from fluid released during the rupture irritating nearby tissue. Some women experience this every month, others only occasionally, and many never notice it at all.
Basal body temperature shift. After ovulation, your resting body temperature rises slightly, typically less than half a degree Fahrenheit (between 0.4°F and 1°F). The catch is that this shift only confirms ovulation has already happened, so it’s more useful for understanding your cycle pattern over several months than for predicting ovulation in real time.
How to Track Ovulation
If you want to pinpoint when you’re ovulating, you have a few practical options. Over-the-counter ovulation predictor kits test your urine for the LH surge that precedes egg release. Once the test detects elevated LH, ovulation typically follows within 12 to 24 hours. These kits are about 90% reliable when used correctly, according to the FDA, though they tell you whether you’re about to ovulate, not whether you’ll definitely conceive.
Tracking cervical mucus gives you a daily, no-cost signal. When you notice the egg-white consistency, you’re in your most fertile days. Combining mucus observation with temperature tracking and calendar counting gives a more complete picture, since each method covers a different part of the timeline. Mucus and LH tests warn you ovulation is approaching, while temperature confirms it happened.
For a rough estimate without any tracking, ovulation generally occurs about 14 days before your next period. If your cycle is consistently 28 days, that puts ovulation around day 14. But cycles vary, and even women with regular periods can ovulate a few days earlier or later than expected in any given month.
When Ovulation Doesn’t Happen
Not every cycle produces an egg. Anovulation, the absence of ovulation, is common enough that it accounts for roughly 30% of infertility cases. Irregular or missing periods are the most visible sign, though some women with anovulation still bleed on a schedule, making it harder to detect without testing.
The most frequent causes are hormonal imbalances. Polycystic ovary syndrome (PCOS) is one of the leading ones, disrupting the hormonal signals that trigger egg release. Having a very low body weight, whether from restrictive eating or excessive exercise, can also shut down ovulation because the body doesn’t have enough energy reserves to support a pregnancy. Primary ovarian insufficiency, where the ovaries stop functioning normally before age 40, is another cause. And as women approach menopause, anovulatory cycles become increasingly common as part of the natural transition.
If you’re having cycles shorter than 21 days, longer than 35 days, or skipping periods entirely, these patterns suggest ovulation may not be occurring regularly. Tracking methods like LH testing or basal temperature can help confirm whether you’re actually ovulating each cycle, which is useful information to bring to a healthcare provider if fertility is a concern.