During ovulation, one of your ovaries releases a mature egg into the fallopian tube, where it can be fertilized by sperm. This event typically happens once per menstrual cycle, around the midpoint, and the entire release takes only a few minutes. But the hormonal buildup that triggers it starts days earlier, and the changes it sets off in your body last for about two weeks afterward. Here’s what’s actually going on at each stage.
The Hormonal Buildup Before Release
Ovulation doesn’t happen spontaneously. It’s the result of a carefully timed hormone sequence that begins in your brain. Early in your cycle, your pituitary gland releases follicle-stimulating hormone (FSH), which prompts several small follicles in your ovaries to start growing. Each follicle contains an immature egg. Over roughly a week, one follicle outpaces the others and becomes the dominant follicle, while the rest break down and are reabsorbed.
As the dominant follicle grows, it produces rising levels of estrogen. When estrogen reaches a critical threshold, it triggers a sharp spike in luteinizing hormone (LH) from the pituitary gland. This LH surge is the final signal. Ovulation occurs roughly 36 to 40 hours after that surge begins, which is why home ovulation test kits detect LH in urine to predict when release is imminent.
What Happens at the Moment of Release
The dominant follicle, now about 2 centimeters across, sits near the surface of the ovary. The LH surge causes enzymes to weaken the follicle wall, and the follicle eventually ruptures. The egg, along with surrounding fluid, is expelled from the ovary’s surface.
The egg doesn’t simply drop into your fallopian tube on its own. Finger-like projections at the end of the fallopian tube, called fimbriae, actively sweep toward the ovary in response to hormonal signals. Tiny hair-like structures lining these projections beat rapidly in the direction of the uterus, catching the egg and guiding it into the tube. From there, the egg begins a slow journey toward the uterus, propelled by muscular contractions in the tube wall and the rhythmic motion of those same tiny hairs.
At the moment of release, the egg is frozen partway through its final stage of cell division. It will only complete that process if a sperm successfully penetrates it. If fertilization doesn’t occur, the egg simply breaks down.
How Long the Egg Survives
A released egg lives for less than 24 hours. This is a surprisingly narrow window, and it’s one reason timing matters so much for conception. Sperm, by contrast, can survive in the reproductive tract for up to five days. That means the most fertile window actually starts several days before ovulation, not on the day of release itself. If sperm are already present in the fallopian tube when the egg arrives, fertilization is more likely than if intercourse happens after ovulation.
What Your Ovary Does Afterward
Once the egg is gone, the ruptured follicle doesn’t just disappear. It collapses and transforms into a temporary structure called the corpus luteum, a saffron-yellow mass of cells that forms where the follicle once was. This new structure immediately begins producing progesterone and estrogen, two hormones that prepare the uterine lining for a potential pregnancy.
Progesterone thickens and stabilizes the lining, making it rich with blood vessels and nutrients. If a fertilized egg implants in the uterus, the corpus luteum continues producing progesterone for several weeks until the placenta takes over. If no implantation occurs, the corpus luteum breaks down after about 10 to 14 days, progesterone drops sharply, and the uterine lining sheds. That’s your period.
Physical Signs You Can Notice
Your body gives several signals around the time of ovulation, some subtle and some quite noticeable.
Cervical mucus changes. In the days leading up to ovulation, rising estrogen transforms your cervical mucus from thick and sticky to clear, stretchy, and slippery, often compared to raw egg whites. This consistency makes it easier for sperm to travel through the cervix. You typically get this slippery mucus for about three to four days. In a 28-day cycle, that usually falls around days 10 to 14.
A slight rise in body temperature. After ovulation, the progesterone produced by the corpus luteum raises your resting body temperature by 0.3°C to 0.7°C (roughly half a degree to just over one degree Fahrenheit). This shift is too small to feel but can be tracked with a sensitive thermometer each morning before getting out of bed. Because the rise happens after ovulation, basal body temperature tracking confirms that ovulation already occurred rather than predicting it in advance.
Mid-cycle pain. Some people feel a twinge or cramping on one side of their lower abdomen around the time of ovulation. This sensation, sometimes called mittelschmerz (German for “middle pain”), has two likely causes: the stretching of the ovary’s surface as the follicle grows, and the irritation of the abdominal lining when fluid or a small amount of blood escapes from the ruptured follicle. It can last anywhere from a few minutes to a couple of days and typically alternates sides from cycle to cycle, depending on which ovary ovulates.
When More Than One Egg Is Released
In some cycles, both ovaries release an egg, or one ovary releases two. This is called hyperovulation, and one older study estimated that about 20% of people who menstruate have the capacity for it. When two eggs are fertilized, the result is fraternal (non-identical) twins.
Several factors make hyperovulation more likely. Genetics play a role, which is why fraternal twins often run in families. Age matters too: teenagers with still-maturing hormonal systems and people nearing the end of their reproductive years both tend to produce more FSH than usual, which can stimulate multiple follicles. Stopping hormonal birth control can also trigger a temporary period of hyperovulation as the body readjusts to producing its own hormones without suppression.
Both eggs are released within the same 24-hour window. Your body doesn’t ovulate again later in the same cycle, because the progesterone from the corpus luteum suppresses further follicle development until the next cycle begins.