What Are the Chances of Getting Pregnant After One Time Unprotected?

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Learn how ovulation can affect the likelihood of pregnancy after sex

Co-authored by Bedsider and Dan Hickey

Last Updated: November 6, 2025 Fact Checked

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• What are the chances?
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• About Fertility & Ovulation
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• Signs of Ovulation
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• If You Don’t Want to Get Pregnant
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• If You Want to Get Pregnant
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• Pregnancy Prevention Methods

|Show more |Show less

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Your chance of getting pregnant after having unprotected penis-in-vagina sex one time greatly depends on where you are in your menstrual cycle. We’ve partnered with the birth control and sex education experts at Bedsider to get the facts on how likely pregnancy is after unprotected sex, how exactly pregnancy happens, how to tell if you’re ovulating, and more.

Likelihood of Pregnancy after Unprotected Sex

You are more likely to get pregnant after unprotected penis-in-vagina sex if it’s around the time of month that you’re ovulating. On average, the closer it is to ovulation day, the higher the chance you have of getting pregnant. After ovulation day, the likelihood of pregnancy goes down significantly, although there’s still a chance.

• 5 days before ovulation: 9% chance
• 4 days before ovulation: 18% chance
• 3 days before ovulation: 27% chance
• 2 days before ovulation: 33% chance
• 1 day before ovulation: Up to 42% chance
• On ovulation day: 20% chance
• 1 day after ovulation: 8% chance

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Section 1 of 6:

Chances of Pregnancy After Unprotected Sex

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   There’s about a 1 in 5 chance of getting pregnant if you have unprotected sex on the day you ovulate. Ovulation is when your body releases an egg from your ovary, making it possible for a sperm to fertilize it. Studies show there is around a 20% chance of getting pregnant if you have unprotected sex just once on ovulation day. However, it’s tricky to detect exactly when ovulation happens, and the egg is only able to be fertilized for 12–24 hours once it’s released, also making this window difficult to predict.

   • If you have unprotected sex after ovulation, your chances of pregnancy are lower (about 8% one day after ovulation and even lower the next day).
   • Your chances may be higher if you have unprotected sex during or, especially, right before ovulation.
   • If you have unprotected sex more than once around ovulation, your chances of getting pregnant increase. All ejaculate contains millions of sperm, and it only takes 1 to conceive. So, the more sex you have, the greater the chances of pregnancy.
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   There’s a 32–42% chance of getting pregnant if you have unprotected sex the day before ovulation. The day before ovulation is actually when your chance of getting pregnant after unprotected sex is the highest. One study analyzing data from a self-reported fertility tracking app found the odds as high as 42% for people who had unprotected sex on this day. However, some point out that people may underreport the amount of sex they are having, and so the chances may be slightly lower, likely around 32%.
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   There’s a 9–33% chance of getting pregnant 2–5 days before ovulation. The 5 days before ovulation make up most of your fertile days (in addition to the day of ovulation and the 24 hours afterward). There’s around a 9% chance of getting pregnant after unprotected sex 5 days before ovulation, and the percentage increases as you get closer:

   • 4 days before: 18% chance
   • 3 days before: 27% chance
   • 2 days before: 33% chance
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   Chances of pregnancy range from 0–3% outside of the fertile window. Although less likely, it’s not impossible to get pregnant after unprotected sex outside of your most fertile days. Chances drop close to 0% (but not exactly 0%) two days after ovulation, and only rise to about 3% seven days before ovulation.

   • There’s a common myth that you can’t get pregnant during your period. While people with regular periods (menstrual cycles lasting 26–32 days) are much less likely to get pregnant on their period, it’s not impossible.
   • Those with shorter or irregular period cycles are more likely to get pregnant during or right after their periods since there is less time between the period and ovulation.
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Section 2 of 6:

How Fertility & Ovulation Work

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   Fertilization happens when sperm fertilizes an egg. The main way for this to happen without medical intervention is through vaginal intercourse (penis-in-vagina sex). After ejaculation, sperm swim towards the uterus and fallopian tubes where an egg might be. (This is why you can’t get pregnant through oral or anal sex.) Fertilization usually happens in a fallopian tube. Once an egg is fertilized, the embryo travels to the uterus and implants itself in the uterine lining.

   • Pregnancy doesn’t begin until the fertilized egg implants itself in the uterine wall. It takes about a week after fertilization for this to happen.
   • It is common for fertilized eggs to fail to implant and you pass them naturally with your cycle.
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   Where you are in your menstrual cycle determines how easily fertilization may happen. First, let’s go over a quick recap on menstrual cycles and timing. Day 1 of a period is also day 1 of a menstrual cycle. It’s normal for most people with a uterus to have cycles lasting between 21 and 35 days, but having a regular menstrual cycle means that your cycle is between 26 and 32 days long. If your menstrual cycle is regular, your cycles are close to the same length every month, and ovulation happens around the same day every cycle. But it’s also normal to have periods that aren’t all exactly the same number of days.

   • Period bleeding typically lasts 3–7 days and is when the uterine lining sheds and exits the body through vaginal bleeding. It’s unlikely, but not impossible, to get pregnant during this time.
   • After a period, the body begins preparing again to release an egg. This is called the follicular phase. Releasing an egg is called ovulation, and in a 28-day cycle, it happens between days 12 and 16.
   • The most fertile days in a cycle include the 5 days before ovulation, as well as the 24 hours after ovulation. The day before ovulation is when the chances of getting pregnant are the highest.
   • After ovulation, an egg is able to be fertilized for up to 24 hours. If fertilized, the egg will travel to the uterus to implant. If fertilization does not occur, the egg will break down, and the uterine wall will shed to begin the next menstrual cycle.
   • It’s unlikely, but not impossible, to get pregnant after ovulation until the next menstrual cycle.
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   Sperm can live inside the body for up to 5 days. This is why the timing of sex and your menstrual cycle come into play. It’s difficult to know exactly when you’re ovulating (especially if you have an irregular period), so it’s possible to have sex, not ovulate until 5 days later, and then become pregnant. This is why the 5 days leading up to ovulation are typically your most fertile and when it’s most likely to get pregnant. If sperm are already present when an egg is released, the chances of fertilization are higher.
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   Other factors, like age, also impact how easy it is to get pregnant. It isn’t just timing that affects how likely a pregnancy is. For example, fertility declines with age, and some people over 35 may have a more difficult time getting pregnant. The age of the person contributing sperm, on the other hand, doesn’t have as much of an effect on fertility. Other factors that impact the likelihood of pregnancy include:

   • The quality and health of the sperm.
   • Abnormal hormone levels or physical conditions within the reproductive system from cysts or polyps, scar tissue, fallopian tube blockages, or conditions like endometriosis.
   • Sexually transmitted infections (STIs), like chlamydia or gonorrhea.
   • Early menopause.
   • Lifestyle habits like smoking, heavy drinking, excessive caffeine, excessive strenuous exercise, or exposure to environmental toxins.
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Section 3 of 6:

How to Tell If You’re Ovulating

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1. 
   Track your menstrual cycle and look for other signs to estimate when you’re ovulating. If your cycle is regular, keep track of which day you’re on with a calendar, fertility tracker, or tracking app. Ovulation is most likely to occur during the midpoint of your cycle, or days 12 to 16 after your period started. However, this is just an estimate, and things get even trickier if your period is irregular. To be more confident in predicting ovulation, it’s best to also look for signs like:

   • Changes in cervical mucus. This mucus is thick, white, and dry before ovulation, but turns clearer and more slippery just before ovulation happens.
   • An increase in basal body temperature. Your body temperature rises 0.5 to 1 degrees during ovulation. Use a thermometer meant for measuring basal body temperature (your temperature after a period of rest) first thing in the morning before you get out of bed and before you eat or drink anything.
   • Changes in hormone levels. Just before ovulation, there is a surge of estrogen and luteinizing hormone (LH). An ovulation predictor kit (OPK) can detect these surges.

Section 4 of 6:

What to Do if You Don’t Want to Get Pregnant

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   If you’ve had unprotected sex and don’t want to get pregnant, use emergency contraception (EC) within 5 days of having sex. If you’ve had unprotected sex without any other form of contraception within the last 5 days, EC is an effective way to prevent pregnancy (the sooner you take it after sex, the more effective it will be). EC pills work by delaying ovulation, so there is no egg released during a time when sperm may be present. EC does not end a pregnancy that has already begun.

   • Options include over-the-counter medication like Plan B (the “morning after” pill) or prescription EC from a healthcare professional.
   • Can an IUD be used for emergency contraception? Yes! Bedsider explains the details on TikTok here.
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   If you take emergency contraception and you don’t get a period within 3 weeks, take a pregnancy test. You can take a pregnancy test with an at-home urine test or at a visit with a health care provider. Generally, you need to wait at least 10 days after unprotected sex to get an accurate result from a urine test (at home or at a doctor’s office). Urine pregnancy tests are most accurate first thing in the morning.

   • If you go to a health care provider for a test, consider getting tested for STIs. You can often get tested using the same urine sample you leave for the pregnancy test.
   • If the pregnancy test result is positive and someone does not want to be pregnant or parent a child, it is important to know there are safe options for abortion services and resources for adoption services.
   • Abortions may be available with medication or an in-clinic procedure. Medication abortions can be an option earlier in pregnancy.
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Section 5 of 6:

What to Do if You Want to Get Pregnant

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1. 
   Begin having regular sex during your fertile days. A few days after your period ends, start having sex daily or every other day (or every 2 to 3 days if you can’t or don’t want to have sex that often). This increases the likelihood that viable sperm are present on ovulation day and gives you the highest chance of getting pregnant. Continue this schedule through the 24 hours after ovulation.

   • When can you take a pregnancy test? Typically, you’ll have to wait about 10 days after sex to get an accurate pregnancy test result. That’s about how long it takes for the pregnancy hormone called human chorionic gonadotropin (hCG) to reach testable levels (at home or at a clinic).
   • If you’re pregnant, congratulations! Your next step is to visit a health care professional to begin prenatal care.
   • If you’re not getting pregnant and you’d like to be, visit a health care professional or fertility specialist for guidance.

Section 6 of 6:

Pregnancy Prevention Methods

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   There are different options available for ongoing pregnancy prevention. Some people use fertility awareness methods (FAMs) to lower the chance of pregnancy around ovulation. FAMs involve tracking your fertility throughout the menstrual cycle and using non-hormonal birth control methods to avoid pregnancy. These can include not having vaginal intercourse before or during ovulation, using the pull-out method (withdrawal), using vaginal gels or a barrier method like using condoms or internal condoms.

   • These methods are typically 77–98% effective at preventing pregnancy but can be hard to use without making occasional mistakes (like accidentally having unprotected sex on a fertile day).
   • These methods also require communication and commitment from sexual partners for the best results.
   • Does pulling out work? Yes, when done correctly. Watch an explanation from a Bedsider expert on TikTok here.
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   Some people opt for ongoing contraception for more peace of mind. The IUD and the implant both work very well to prevent pregnancy and can be used for between three and twelve years, depending on the method. The pill, patch, ring, and shot are also highly effective birth control methods. Procedures like tubal ligation (getting your “tubes tied” if you have a uterus) or a vasectomy (for people with testicles) are also permanent birth control options.

   • To figure out which birth control method might work best for you, check out this method explorer from Bedsider to compare effectiveness, side effects, STI protection, cost, and more.
   • Not sure where to start with contraception? A great first step is to speak with a healthcare provider (in person or virtually). Here are some resources, courtesy of Bedsider:
     • Find a health center (for birth control prescriptions, STI testing, and other in-person reproductive services)
     • Get birth control online (to get birth control prescriptions delivered to your home)
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