After ovulation, your egg survives for about 24 hours. That’s it. If sperm doesn’t reach and fertilize the egg within that narrow window, the egg dissolves and gets reabsorbed by your body. This short lifespan is why timing matters so much when you’re trying to conceive, and why your actual fertile window is shaped more by sperm survival than by the egg itself.
What Happens to the Egg After Release
When your ovary releases an egg, it enters the fallopian tube, which is where fertilization typically happens. Sperm that have already traveled into the fallopian tubes wait there for the egg to arrive. If fertilization doesn’t occur within roughly 24 hours, the egg begins to break down. It dissolves right there in the reproductive tract and is reabsorbed by your body. You won’t feel this happen or notice any sign of it.
Meanwhile, the structure left behind on the ovary (called the corpus luteum) keeps working for about 10 days after ovulation. It pumps out progesterone, which thickens your uterine lining in preparation for a possible pregnancy. If no fertilized egg implants, the corpus luteum breaks down, progesterone drops, and your period starts. That hormonal timeline explains why there’s usually a consistent 10 to 14 day gap between ovulation and your next period, even though the egg itself was only viable for a single day.
Why the Fertile Window Is Longer Than 24 Hours
If the egg only lasts a day, you might wonder why doctors talk about a fertile window of up to six days. The answer is sperm. Sperm can survive inside the cervix, uterus, and fallopian tubes for three to five days. That means sex several days before ovulation can still result in pregnancy, because the sperm are already in position when the egg finally appears.
The American Society for Reproductive Medicine defines the fertile window as the six-day interval ending on the day of ovulation. In a study of 221 women, the highest chance of conception came from intercourse within the two days before ovulation. Interestingly, the probability of pregnancy already starts to decline when intercourse happens on the day of ovulation itself, likely because the egg’s 24-hour clock is already ticking by that point and sperm need time to reach the fallopian tube.
So the practical takeaway: the egg’s short lifespan means that sex after ovulation has a much smaller chance of leading to pregnancy than sex in the days leading up to it.
How to Know When Ovulation Happens
Pinpointing the exact moment of egg release is tricky because it’s an internal event with no obvious signal. But your body does offer some clues.
Ovulation predictor kits measure the surge of luteinizing hormone (LH) in your urine. Once LH surges, ovulation typically follows about 36 to 40 hours later. This makes LH tests one of the more useful tools because they give you advance notice rather than confirmation after the fact.
Basal body temperature tracking works differently. Your resting temperature rises slightly after ovulation, so you can confirm that ovulation happened. The catch is that by the time you see the temperature shift, ovulation is already underway or complete. That means BBT tracking is better for understanding your cycle patterns over several months than for catching the fertile window in real time.
Cervical mucus changes can also help. In the days before ovulation, mucus tends to become clearer, stretchier, and more slippery. This shift happens in the lead-up to egg release, making it another forward-looking signal you can pair with other methods.
Age and Egg Quality
The 24-hour survival window doesn’t change much with age, but egg quality does. As you get older, the eggs your ovaries release are more likely to have chromosomal issues, which reduces the chance of successful fertilization and healthy implantation even if sperm reaches the egg in time. Eggs that aren’t released during any given cycle simply die and get reabsorbed, a process that happens continuously throughout your reproductive years. By the time you reach menopause, your egg supply is essentially depleted.
Making the Most of a Small Window
Because the egg’s viable period is so short, the most effective strategy for conception is having sperm already waiting in the fallopian tubes before the egg arrives. That means the two to three days before ovulation are your highest-probability days. Having sex every day or every other day during that window gives sperm the best chance of being in the right place at the right time.
If you’re tracking your cycle, combining LH test strips with cervical mucus observations gives you both a biological signal and a hormonal one, which together narrow down your timing more reliably than either method alone. Once you’ve confirmed ovulation through a temperature shift, the fertile window for that cycle has already closed or is closing rapidly. The egg is on its 24-hour countdown, and within a day it will dissolve if unfertilized.