Odds of Getting Pregnant: Pregnancy Probability Statistics

What are the odds of getting pregnant? The probability of pregnancy is a common concern for both those trying and trying not to conceive, and unfortunately, that’s not a simple question.  Worse, most folks don’t want just a “not likely” or “probably.” They want a number. A statistical chance of pregnancy. Here at Life with Gremlins we have a page explaining the basics of how to get an idea of your odds of getting pregnant. We even have a quiz that will give you an answer on a continuum from no chance to high, but in an effort to give you that specific number you’re looking for, now we’re going to delve into the complicated world of conception statistics.

Where to start? Well, how about when you did, intercourse timing.

Odds of getting pregnant by intercourse timing:

The fertility window is from 5 days prior to ovulation up to ovulation itself. However, it’s important to note this is based on the fact that while most studies agree sperm remain viable up to 5 days (but are most viable in the first 48 hours), research on the egg’s survival range is more conflicting. The mean viability of an egg is generally accepted at 12 hours (the point where in 50 percent of cases, the egg is still viable). However, on the early side, an egg may only survive mere hours and on the late—and longshot— a rare egg may make it a full 48.

The most complete study done on the odds of getting pregnant on any given day was done in 2013 and published in the Oxford Journal of Human Reproduction. While it’s findings ran similar to others done on the topic, it was the first to counter in maternal age, cycle regularity, and ethnicity. It presented two sets of data, one simply factored in cycle day and ignored ovulation date. The other was based off the probability of pregnancy depending on when in the fertile window intercourse was. I know, this seems quite confusing, for example, one graph shows that the maximum chance of pregnancy occurs on day 15 at 13.1 percent. However, the other graph shows a maximum chance of 36 percent the day of ovulation.

Why the difference? 

The second, much higher statistic is guaranteeing the sex occurred in a fertile period. So, with data set one, the percentage is skewed by the chance that sex didn’t occur during a fertile time. For example, a woman has a condom break on day 15 of her cycle. There is a 13.1 percent chance that she is both fertile and will become pregnant. Now, assume that she knows she also ovulated that day, now there’s just a 36 percent chance of pregnancy—we already know she’s fertile.

Why am I giving you both?

Data set one is going to be most useful to those who aren’t really trying to conceive and have no idea when they ovulate. The quick and dirty of it is that the odds of getting pregnant begin close to 0, and then rise around cycle day 7 (with day 1 being the first day of bleeding). They reach a peak at day 15 followed by a slow decline to close to 0 after day 25. This is because most people ovulate around mid-cycle and the average cycle length is between 28-30 days (hence days 13-16 have the highest chance of pregnancy).

Data set two is going to be more useful to those who are trying to conceive and are entirely sure what day they ovulated.
odds of getting pregnant by cycle day odds of getting pregnant by days from ovulation

Take away: Considering the high probability of slight miscalculation when predicting ovulation (even with BBT and cycle tracking) most sources average it out to a 20 to 25 percent chance of pregnancy when sex is mid-cycle.

Timing is far from the only factor in the odds of getting pregnant though, for instance, the chances of pregnancy also change with age.

The chances of getting pregnant by age:

In the graph above you see little change between women under 25 and those over 35, but when you look at the percentage of women who became pregnant within a year of trying, the difference becomes clearer. This is a result of declining egg reserve and quality.

odds of getting pregnant by age

Take away
: In your late 30’s the odds of getting pregnant begin to decline, dropping more dramatically after 40. The vast majority of women under 35 will become pregnant with monthly unprotected sex within one year.

Timing and age are the two primary drivers behind the odds of getting pregnant in general (excluding genetics, which is impossible to factor with a wide audience like this. ) Of course, many smaller health issues can play a big role as well. We can’t possibly cover them all, but will try to touch on some of the more common issues.

Factors that can affect your overall odds of getting pregnant further:

-BMI: The chances of natural conception reduce 26 percent in those with a BMI over 35, and 46 percent in those with a BMI over 40. Being underweight likewise reduces the chance of pregnancy, with a 37 percent decrease for those with a BMI under 20.

-PCOS: Often holding hands with a high BMI, PCOS is a hormonal condition that usually results in anovulatory cycles and ovarian cysts. Weight gain, facial hair, thinning hair at the top of the head, and irregular periods are the most common symptoms. Around 10 percent women of reproductive age suffer from PCOS, and roughly 80 percent of those women are left infertile.

-Smoking: While research is still conflicting, some studies have found active smokers have 50-percent lower odds of getting pregnant each month.

Activity level: Those who exercise moderately for at least 5 hours a week have an estimated 18 percent higher chance of conception. However, vigorous exercise (more than 5 hours a week, intense workouts) creates a roughly 32 percent lower chance of conception. The exception to this was in women who were overweight, in which case fertility often returns with diet, exercise, and weight loss. Less than 5 hours of exercise a week has no effect on fertility.

The male factor:

Obviously, it takes two to become pregnant, and while this website is predominantly visited by women, the other half of the equation can’t be ignored when it comes to pregnancy probability.

Age is the most predominate factor in the odds of getting pregnant based on a partner. Men are thought to be most fertile from about age 25 to 29. A 2004 study by the American Journal of Gynecology found that the chances a male will conceive a child within a year of trying drops by 11 percent per year. This means that the older a male partner is, the lower the odds of getting pregnant in most cases. Regardless, as a result of age alone, men never cease producing sperm. The oldest known man to father a child was 102 years old.

Other factors on male fertility are less generalized. Things such as environmental exposure to heat or  toxins,  testicular trauma, genetics, and some health conditions can reduce fertility in younger men.

Next we’ll have a look at situational factors in the odds of getting pregnant, first with the chances of getting pregnant from precum, but as we are already at over 1,200 words, we’ll split that into it’s own page.

PMS or Pregnancy Symptoms: What’s the Difference?

pms or pregnancy period or pregnantMost of us are aware of what pregnancy symptoms are. The media has shown us pregnancy is this obvious in-your-face change. In reality though, pregnancy symptoms can be far more subtle. Things like nausea, bloating, breast tenderness, discharge changes, food aversions/cravings, flatulence, mood swings, hot sweats, frequent urination, fatigue, and more can vary in severity. Of course, don’t some women get those same symptoms just before their period? Why is that? Is your body telling you pregnant or period? How can you judge, PMS or pregnancy?

What causes PMS or pregnancy symptoms?

The first question there comes down to understanding what causes both pregnancy symptoms and PMS, because the culprit is the same—hormones. In fact, it’s even the same hormone for the most part.

The second half of your menstrual cycle after ovulation (the luteal phase) is dominated by a hormone called progesterone. Progesterone’s job is to maintain the uterine lining for pregnancy before implantation and during pregnancy afterwards. It’s present in both pregnant and non-pregnant women. Progesterone concentration just becomes higher in early pregnancy. High progesterone can cause nausea, bloating, breast tenderness, discharge changes, food aversions/cravings, flatulence, mood swings, and hot sweats—a fair chunk of pregnancy symptoms. Essentially, pregnancy symptoms are just PMS on steroids, because progesterone levels are higher and also slowly joined by hCG (Human chorionic gonadotropin). hCG is the hormone that causes a pregnancy test to become positive, by the way.

So, how can you tell if it’s PMS or pregnancy then?

While there are a few pregnancy symptoms that are uncommon in PMS (frequent urination and fatigue), all sorts of things can cause those symptoms from the flu to a hot day. The real settling factor is actually time. Pregnancy symptoms won’t occur before a missed period unless you have an irregular cycle or a very long cycle. That’s the truth. There is absolutely no reason to stress over symptoms before a minimum of 8 days after ovulation or intercourse if you don’t know when you ovulated. As PMS occurs before your period, in almost all cases unless your period is late, your symptoms are PMS.

I know, especially for folks trying to conceive that is a hard answer to swallow, but hear me out. For your symptoms to be pregnancy related, you have to be pregnant. It takes a minimum of 6 days for an egg to travel and implant (making you pregnant), but the average is 8 to 10 days. After that, it takes time for hormone levels related to pregnancy to begin to rise (higher progesterone and hCG). You can’t even get a positive pregnancy test for about 48 hours plus.  With the average menstrual cycle at about 28 days, and ovulation frequent at mid-cycle, this means for the average cycle you aren’t even pregnant until the question of PMS or pregnancy becomes a moot point. This is why I recommend whether you’re hoping to be pregnant or praying you aren’t after an oops, that you disregard symptoms entirely until your period is due. If you’re more than 3 days late (3 days +/- is considered normal period variance), then just take a test. It’s a far easier answer than trying to analyze your symptoms and a lot less stressful.

What if your period is late or have long/irregular cycles?

Now there is an exception to that rule. In those that have irregular or long cycles, ovulation is often erratic. In which case, there may not be a firm period due date or periods may already be absent. Second, it is possible to have a late period without being pregnant. We also have a full page on missed periods with a negative test here. In both case timing goes out the window and a pregnancy test is going to be the only answer for you. If your symptoms are pregnancy related, unless you are much further along than you think you are, a pregnancy test will reflect that.

You might also find helpful:
When to Take a Pregnancy Test for Accurate Results
In-Depth: When Do Pregnancy Symptoms Start at the Earliest?
Early Pregnancy Symptom Quiz

When Do You Ovulate? Ovulation Symptoms, Prediction Tools, and Timeline

Ovulation—it’s like the holy grail of conception. You can’t get pregnant if you can’t figure out if and when it happens to you, sort of. I mean, you can actually take a cheater’s approach and just have sex every other day or so around mid-cycle. That’s when ovulation occurs for most. So, you’d think all you have to do is take your cycle length and cut it in half. Bam—estimated ovulation date. The problem there is, while easier, this approach is sort of shooting in the dark—but with sperm—and while that can be fun it can make conceiving take a while, because not all women ovulate mid-cycle. In fact, some women don’t ovulate at all. So, if getting pregnant quickly is your aim, when do you ovulate should be your first question.when do you ovulate

What is ovulation?

Chances are if the Google Gods led you to this page, you have at least a fuzzy idea what ovulation is, but for clarifications sake, ovulation is the point during your menstrual cycle when your ovary drops a fertile egg. You can only become pregnant in those 24 hours or so after ovulation while that fertile egg is in your fallopian tube. If sperm isn’t present in that time frame, the egg is shed along with your uterine lining during your period.

When do you ovulate?

As mentioned above, most women ovulate around mid-cycle. Dividing your average cycle length by two is a fair way to get a rough estimate of when you ovulate.

Example/ If you have a 26-cycle, you probably ovulate around cycle day (CD) 13 with day one being the first day of active bleeding during your menstrual cycle.

You can narrow this down to an average for you personally (I, for example, run a 26-day cycle, but ovulate around CD 11) by tracking your ovulation symptoms, utilizing basal body temperature (BBT) tracking, and ovulation predictor kits (OPKs). When trying to pinpoint ovulation, I then recommend the following tools for your conception toolkit:

-A good BBT thermometer. A regular thermometer will not give an accurate temperature shift. BBT can be used to confirm ovulation. I’ll talk a bit more about that here in a moment. I also have a full, more in-depth guide on how to track BBT here.

-An easy to use tracking app. I use FertilityFriend, but there are many combination BBT, signs of ovulation, and period trackers out there. You can also keep track on paper, but most find an app more convenient. For beginners apps can also prove easier, because they often will estimate ovulation for you based on the data you enter.

-A supply of inexpensive ovulation predictor kits. OPKs can be used to predict ovulation shortly before it happens. We will also cover that how in just a moment.

Ovulation symptoms: What are the signs of ovulation?

To understand ovulation symptoms and when and why they happen, it’s best to have a rough understanding of the hormones that drive your menstrual cycle. It’s these hormones that are behind most signs of ovulation.

At the start of your cycle (the first day of bleeding) your sex hormones (estrogen and progesterone) are both low. This signals the release of Follicle Stimulating Hormone (FSH). FSH is what prompts a follicle in your ovary to develop an egg. The development of this egg stimulates estrogen production which is the dominate hormone before ovulation in the follicular phase of your cycle. High estrogen then triggers Luteinizing Hormone (LH) to be produced. LH is the hormone that triggers ovulation. Ovulation stimulates the production of Progesterone, which dominates the second half of your cycle, the luteal phase. Progesterone maintains the uterine lining, and will drop if the released egg isn’t fertilized or continue to rise if it is.

Ovulation discharge:

Keeping the above cycle in mind, those hormones cause different cervical discharge changes. At the beginning of your cycle as estrogen is low, your discharge is probably non-existent to light, dry or sticky and acidic. This discharge is not very sperm friendly, but it does deter bacteria growth to protect your vagina from infection.

As estrogen begins to rise discharge becomes wetter, less acidic, and more plentiful (more fertile) finally reaching a stretchy, jelly-like consistency often described as “egg-white.” Egg-white discharge is a sign of ovulation.

when do you ovulate fertile cervical mucusFollowing ovulation as estrogen decreases and progesterone rises discharge often goes back to watery, followed by sticky or dry, and then bleeding if you don’t become pregnant. Some women also see an increase in discharge just before their period, and some women see watery discharge all cycle. It’s the stretchy mucus you’re watching for. On another note, thick yellow discharge at the end of your cycle can also sometimes be an early sign of pregnancy.

Cervical position and state:

Cervical position is a harder sign of ovulation to track. Your cervix actually moves up and down during the day, but if you check it at the same time every day, you may also notice a pattern within your cycle. Like your discharge, your cervix is affected by your hormones. During periods of low estrogen the cervix remains low, long, hard, and closed. You’ll probably be able to easily reach it, and it will feel sort of like the tip of your nose. As estrogen rises, the cervix does too, becoming shorter, softer, and opening slightly (note that those with previous children often always have a slightly open cervix). During ovulation your cervix will be hard to reach and feel more like your lips. Many women remember the signs of ovulation in regards to cervical position and state with the abbreviation SHOW: soft, high, open, wet (mucus).

when do you ovulate cervical position


Ovulation predictor kits are, like a pregnancy test, a stick that you urinate on. They detect LH which surges about 24 to 48 hours before ovulation. It’s important to note that unlike a pregnancy test, an ovulation test is only positive if the test line is darker than the control line. LH is present in your system outside of ovulation, so there will almost always be two lines. If you have trouble reading the cheaper line tests, there are more obvious (and expensive) smiley-face tests available. You don’t have to use these tests all cycle, just during your ovulation window. Until you narrow down your window more, I recommend starting at about CD 8. You can stop after ovulation. We also have a complete guide on using OPKs.

Ovulation pain:

Ovulation pain is not something everyone gets. In fact, only about 1 in 5 women experience pain at ovulation. Many describe ovulation pain as a twitching, pinching, or pressure in their lower pelvis closer to the right or left hip (this is where your ovaries are located). Ovulation usually occurs from just one side, and may not occur on the same side every month. If pain is felt on one side near your ovary near when ovulation should occur, you can consider it a sign that ovulation may be near or occurring caused by the growing follicle or the rupture of the follicle to release an egg.

However, keep in mind that cramping can often be mistaken for ovulation pain. As a general rule if it’s not lining up with other signs of ovulation or occurs on both sides, it probably is not ovulation pain.

Ovulating spotting:

Like ovulation pain, not all women experience ovulation spotting. Sometimes spotting is caused by the rupture of a follicle to release an egg. To put this in perspective, the average follicle is a mere 18 to 24 mm—or between the size of a dime and a nickle. Ovulation spotting of this type is very light.

Alternately, some women also get a slight hormone dip at ovulation, which can also cause light spotting. In those women, a temperature dip would also be visible on a BBT chart. This bleeding would still not be heavy or prolonged.


You can read a full in-depth guide on tracking your BBT here, but briefly, your BBT is your temperature taken with a BBT thermometer upon first waking in the morning, before doing anything else. The rise of progesterone after ovulation will cause this temperature to rise slightly allowing you to confirm that ovulation has occurred and so build a more concrete average ovulation pattern. This rise is sometimes very small and a clear shift is hard to see. For other women it’s more pronounced and may even be visible using a regular thermometer.

Other signs of ovulation:

Finally, individual women may notice different signs of ovulation. Some women notice they crave certain foods or are more interested in sex. To pick up on signs like these you need to track ovulation for some time and really pay attention to your body. You’ll likely be more aware of post-ovulation symptoms as progesterone is the culprit behind PMS. Things like feeling hot, bloating, nausea, and back pain are all caused by progesterone which peaks after ovulation. This leads me to an important note. It is very, very, and a few more very’s common to mistake PMS symptoms for pregnancy symptoms. You will not get pregnancy symptoms before implantation. Period. You can explore the pregnancy symptoms timeline in more depth here as that is an entirely different topic.

We hope that our guide on when do you ovulate has proved helpful in your quest for belly fruit, and as always, welcome your comments, questions, and suggestions.

You might also find useful:
Conception Lingo
When to Take a Pregnancy Test for Accurate Results
Am I pregnant? Calculating Your Chances of Pregnancy