There is a high chance of becoming pregnant if a person has sex within 12–24 hours after ovulation. A person can conceive at any time, but especially if they have sex from 5 days before until 1 day after ovulation.
Ovulation occurs when one of the ovaries releases a mature egg. This is the time when the body is ready to receive sperm for fertilization.
If fertilization does not occur, the egg disintegrates into the uterine lining. The body will then shed the remains during a person’s monthly period.
Ovulation lasts anywhere from 12–24 hours. After the ovary releases an egg, it survives for about 24 hours before it dies, unless a sperm fertilizes it.
If a person has sex days before or during the ovulation period, there is a high chance of conceiving. This is because sperm can survive up to 5 days in the cervix. Therefore, it is important to understand the fertile window.
The fertile window is the period of time during which it is possible to become pregnant from sex. This is the day of ovulation plus the amount of time that sperm can live inside the cervix before it fertilizes the egg.
According to the American College of Obstetricians and Gynecologists (ACOG), a person can become pregnant if they have sex anywhere from 5 days before until 1 day after ovulation.
Depending on the menstrual cycle, the fertile window may vary from one person to another.
To calculate the fertility window, a person should note the first day of a period until the next period occurs. This timeframe is the menstrual cycle. On average, most people who menstruate have a 28-day cycle.
However, according to the Office on Women’s Health, for some, it may last
According to the ACOG, ovulation occurs around day 14 of the menstrual cycle.
A person with a 28-day cycle, for example, will have their fertile window 5 days before the ovulation date.
Pregnancy is possible 12–24 hours after ovulation. This is because the released egg can only survive 24 hours before the sperm can no longer fertilize it.
The likelihood of getting pregnant on the days before and after ovulation varies from one person to another.
An older study from 1995 looked at the timing of sexual intercourse in relation to ovulation and the likelihood of conception.
Out of 221 healthy women, there were 192 pregnancies. Researchers concluded they could estimate the odds of becoming pregnant on each day of the fertile window as between 10–33%, depending on the day.
| 5 days before ovulation | 10% |
| 4 days before ovulation | 16% |
| 3 days before ovulation | 14% |
| 2 days before ovulation | 27% |
| 1 day before ovulation | 31% |
| Ovulation day | 33% |
The same study authors also note there could be a 12% chance of conceiving on either day 7 before ovulation and the day after ovulation.
However, the chances of becoming pregnant before or after ovulation depend on several factors, including:
- age
- frequency of sexual intercourse
- menstrual cycle
For those trying to conceive, tracking ovulation is crucial to ensure they identify the most fertile days in the menstrual cycle.
Here are some of the methods a person can use to track or predict ovulation.
Basal body temperature charting
Basal body temperature (BBT) is the temperature when the body is at rest.
Charting BBT for a series of months by measuring every morning after waking up will help predict ovulation.
During or when ovulation approaches, there is a slight increase in BBT. A person can use a digital thermometer to track these small changes in temperature.
Monitoring BBT can help tell when ovulation occurs and therefore predict the days in the cycle when pregnancy is possible.
Ovulation predictor kits
Using ovulation predictor kits, such as test strips and digital tests, will help measure the level of luteinizing hormone (LH), which usually rises during ovulation.
A person needs to take tests for consecutive days to detect the rise in LH.
Once they notice a consistent rise, experts recommend having sex daily for the next couple of days to increase the chances of pregnancy.
Cycle charting apps
Several cycle apps, such as the Clue period tracker and Flo period ovulation tracker, can help calculate the ovulation period and fertile window.
Charting ovulation using these apps will indicate the ovulation date and days when a person’s body is most fertile.
Fertility monitors
For people trying to conceive or wishing to avoid pregnancy, using fertility monitors to track ovulation can help people plan intercourse.
Fertility monitors work by measuring significant body changes, such as BBT, heart rate, and breathing.
By compiling this data, the fertility monitor can predict the fertile window.
Cervical mucus method
Observing cervical mucus can give an idea of when a person may be ovulating.
When ovulation approaches, the cervical mucus changes to a thin, clear, stringy, slippery consistency. It may look similar to raw egg whites.
The mucus allows the sperm to swim to the released egg during intercourse.
Ideally, this is the ideal time to have sex due to the high chances of becoming pregnant.
Watching ovulation signs, such as a slight increase in BBT, changes in cervical mucus, and increased sex drive, can help determine the best time to have sex to boost chances of becoming pregnant.
In addition, having sex during the fertile window increases the chances of conception. During this timeframe, the body is ready to receive sperm for fertilization.
On average, a menstrual cycle lasts between 21–35 days.
An irregular cycle or absent cycle that lasts fewer than 21 days or more than 35 days, can mean that a person is not ovulating.
A person should speak with a doctor if they do not become pregnant after 1 year of trying to conceive.
Age may also determine when to seek help. People between 35–40 years of age should speak with a doctor after 6 months of trying to get pregnant. For those above 40 years of age, a healthcare professional may run some fertility tests.
A doctor may also test for possible signs of infertility or if a person has ever had repeated miscarriages, pelvic inflammatory disease, endometriosis, prior cancer treatment, or a history of irregular periods.
A person can get pregnant 12–24 hours after ovulation, as a released egg can survive up to 24 hours within the cervix.
For those trying to conceive, it is crucial to understand the menstrual cycle.
Beyond this, a person can use methods, such as BBT charting, cycle charting apps, fertility monitors, changes in cervical mucus, and ovulation predictor kits to boost the chances of pregnancy.