The menstrual cycle of most women lasts for a total of 28 days. This means that you have approximately six days during each month when you are able to conceive a child. This includes the day that one of your ovaries releases an egg, which is known as ovulation, as well as the five days that come before it. Having sexual encounters during that time frame is essential.
When trying to conceive, it can be helpful to know when ovulation occurs and when a person is most fertile. Some people may wish to track their fertile window to avoid pregnancy.
Females are most fertile within a day or two of ovulation, which is when the ovaries release an egg. But, it is possible to get pregnant in the days leading up to ovulation, as sperm can survive for several days inside the female body.
The days during the menstrual cycle when a person is least likely to get pregnant are known as the ‘safe period.’
This article describes how to calculate the fertile window to aid or avoid conception.
Sex and gender exist on spectrums. This article will use the terms “male,” “female,” or both to refer to sex assigned at birth. Click here to learn more.
The average person’s menstrual cycle is between 28–32 days. Some people have shorter cycles, while others have much longer ones.
The first day of a person’s period is considered the first day of their menstrual cycle. Their period then typically lasts 3–7 days.
Variations in the menstrual cycle usually happen in the follicular phase that occurs before ovulation.
The luteal phase, which occurs from ovulation to the next period, is typically 14 days long.
Learn more about the phases of the menstrual cycle here.
Ovulation occurs when one of the ovaries releases an egg. After release, the egg moves to the fallopian tube, where it will travel to the uterus, which takes about 24 hours.
Pregnancy occurs if sperm travels to the fallopian tube and fertilizes the egg. If sperm does not fertilize the egg, the egg moves to the uterus and breaks down, ready to leave the body during the next menstrual period.
According to the American College of Obstetricians and Gynecologists, ovulation occurs around 14 days before a person expects to have their next period if their monthly cycle is 28 days.
Most people ovulate between days 11–21 of their cycle. The first day of their last menstrual period (LMP) is day 1 of the cycle. Ovulation does not always occur on the same day every month and can vary by a day or more on either side of the expected date.
Doctors call the part of the cycle around ovulation the fertile window because the chance of pregnancy is highest at this time. For example, if ovulation occurs on day 14, a person can conceive on that day or within the following 24 hours.
However, their fertile window begins a few days before ovulation because sperm can survive for up to 5 days inside the female body. So, even if a person does not have sex on day 14 or 15, it is still possible to become pregnant if they had sex without using contraception on days 9-13.
According to research from 2018Trusted Source, the likelihood of conception rises from day 8, reaching its maximum on day 13 and decreasing to zero by day 30.
However, It is essential to note that these findings should only act as a guideline. Every person and every cycle is different.
It can be helpful for a person to chart their monthly cycle and take note of the signs of ovulation to help pinpoint the exact day of ovulation each month.
Signs of ovulation
Tracking the signs of ovulation can help someone determine the precise day they ovulate each month.
- mild cramping in the lower abdomen
- wetter, clearer, and more slippery vaginal discharge similar to egg white
- a small increase in basal body temperature
- a higher sex drive
Some of these signs, such as basal body temperature, will continue to change after ovulation. For this reason, a person should not use temperature to predict the fertile window.
It may be helpful for someone to track the signs over a few months to get an idea of what is typical for their body.
But they should keep in mind that there are several variables, and the timing of ovulation can change, month-to-month.
Another option is to use an ovulation predictor kit or fertility monitor.
Fertility aids measure the levels of specific hormones in the urine to determine the ovulation day each month. Some devices also identify days of peak fertility.
Using a combination of these methods may provide an individual with the best accuracy.
The following table, based on research from 2015, summarizes a typical menstrual cycle and how fertile a person is likely to be at each stage:
|Day of cycle
|least fertile stage
|possible to conceive
|days around ovulation
|possible to conceive
|thickening of uterine lining
|less fertile — unlikely to conceive
To get a more specific range of highest fertility windows based on the day of ovulation, a person can track the first day of their last period in a pregnancy calculator.Trusted Source
To maximize the chances of becoming pregnant, a person should time sexual intercourse to occur during the 2–3 days leading up to, and including, ovulation. Having sexual intercourse on any of these days may provide a 20–30%Trusted Source chance of pregnancy.
Other tips to improve the chances of conception include:
- Have regular sexual intercourse. Pregnancy rates are highest among partners who have sex every 2 or 3 days throughout the month.
- Avoid smoking. Smoking tobacco reduces fertility and impacts the health of a developing fetus.
- Limit alcohol intake. Alcohol intake can reduce fertility in males and females and harm a fetus.
- Maintain a moderate weight. People who have overweight or underweight are more likely to have irregular ovulation.
- Reduce stress: While the research on whether anxiety or stress can reduce fertility is not conclusiveTrusted Source, it is clear that reducing stress can provide some benefit for a person trying to conceive.
- Manage comorbidities: Rule out or treat any medical causes that may contribute to infertility. In females, this can includeTrusted Source hormonal problems, endometriosis, polycystic ovary syndrome (PCOS), uterine fibroids, autoimmune disorders, and more.
A doctor can assess a couple’s overall health and may be able to identify methods to improve the probability of conception.
What can affect male fertility?
Even if a person is having regular sexual intercourse and tracking ovulation, there can be reasons why the sperm cannot reach the egg.
Causes of male infertility include:
- Sperm morphology: Differences in the size and shape of the sperm can impact fertility.
- Low sperm count: The male partner’s ejaculate fluid does not contain sufficient sperm. Fertility doctors consider a person to have a low sperm count if they have under 15 million sperm per milliliter of semen — the fewer the sperm, the lower the chances of conception.
- Low sperm motility: This means the sperm cannot move as efficiently to reach the egg.
There are a variety of medical conditions that can causeTrusted Source any of these problems with male fertility, including a hormonal imbalance, infection or injury to the testicles, surgery in the area, and diseases such as cancer.
Some people may wish to track their fertility to prevent pregnancy. This is known as the fertility awareness method.
The Centers for Disease Control and Prevention (CDC) charts fertility awareness-based methods of contraception as having a 24% failure rate with typical use.
The chances of pregnancy are lowest during a person’s period and on the days on either side of the period.
However, they may still become pregnant if they have ovulated early or late in their cycle, as sperm can survive in the body for several days.
People wishing to use the fertility awareness method should speak with their doctor first.
Ovulation and the fertile window can change from cycle to cycle, but they may also alter with age. Fertility naturally begins to decline in females in their 30s. By age 40, a person’s chance of conceiving drops to 10% per cycle.
The number of eggs and egg quality decrease with age. Ovulation may also become irregular.
Some medical conditions, such as endometriosis or PCOS, also make conception more difficult.
Learn more about PCOS and fertility here.
Birth control pills aim to prevent unintended pregnancy. The pill prevents pregnancy by releasing synthetic hormones that stop ovulation from occurring and the uterus lining from thickening.
So, even if the ovaries do release an egg, a fertilized egg would be unable to implant in the wall of the uterus. The pill also thickens cervical mucus, making it harder for sperm to reach an egg.
According to the CDCTrusted Source, the birth control pill is more than 99% effective with perfect use but only 91% effective with typical use. This means that around 9 out of 100 women would become pregnant in a year of taking the pill with typical use.
Learn more about the pill and its potential side effects here.
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Females who track their fertile window with the aim of getting pregnant should see their doctor for preconception planning.
As well as identifying barriers to conceiving, a doctor can advise on the use of folic acid or prenatal supplements to encourage a safe pregnancy.
Most couples who have frequent sex without contraception will conceive within 12 months.
Women under 35 years of age should see their doctor if they do not conceive after a year of trying. Those over 35 years of age should seek medical advice after 6 months of trying to conceive.
Anyone who has irregular cycles or does not appear to ovulate should also speak with their doctor. There may be an underlying medical cause that is preventing ovulation and conception.
Here are the answers to some frequently asked questions about when pregnancy can occur.
Can I get pregnant 2 days before my period?
Days 17-28 before the first day of a person’s period are the days when the uterine lining begins to thicken. While a person is less likely to conceive during this time, conception is still possible.
Learn more about the uterine lining here.
Can I get pregnant on my period?
Although pregnancy is still possible, a female is less fertile while on their period.
How many days after your period can you get pregnant?
A female can get pregnant at any time during her menstrual cycle. The likelihood of pregnancy is highest during ovulation, which is typically days 10-14.
Intermenstrual bleeding can occur between periods. To pinpoint the start of a menstrual cycle, a female must correctly identify their actual period.
Your Menstrual Cycle and Conception
“There are two phases to the menstrual cycle: the follicular phase occurs before ovulation, and the luteal phase occurs after ovulation,” says Lauren Sundheimer, M.D., MS, FACOG, an OB-GYN practicing in Orange County, California. “Typically, in a 28-day cycle, a woman will ovulate approximately 14 days after the first day of her period.” (Cycle length varies for everyone though. Irregular cycles are common and don’t follow this 28-day pattern.)
The egg that’s released during ovulation survives for only 24 hours. Sperm can survive three to five days in the uterus and fallopian tubes, says Barbara Stegmann, M.D., a triple board-certified OB-GYN and women’s health clinical lead at Organon. Having PIV sex during ovulation or the days beforehand can result in pregnancy, since the egg can meet with existing sperm in the reproductive tract.
But “if the egg is not fertilized by a sperm during this time, it does not survive,” says Michele Hakakha, M.D., a board-certified obstetrician and gynecologist based in Los Angeles and co-author of Expecting 411: Clear Answers and Smart Advice for Your Pregnancy. About 12 to 16 days later, your uterine lining sheds, resulting in your period.
Can Your Get Pregnant Right After Your Period?
For most people, pregnancy isn’t likely to happen right after your period—but it is possible. As early as the third day of your menstrual cycle, your levels of the reproductive hormones progesterone and estrogen, which taper off at the start of your period, begin to climb and help your uterine lining rebuild.
Although an egg isn’t released during in the immediate post-period phase, called pre-ovulation, your chances of conceiving aren’t zero. Sperm can live up to five days in hospitable cervical mucus. That means they can stick around for a few days until your body does release an egg during ovulation—especially if you have a shorter menstrual cycle. “One study showed that people who had sex only one time during this phase still got pregnant,” says Steven R. Bayer, M.D., a Boston-based reproductive endocrinologist.
Here are a few other scenarios that can lead also to conception immediately after menstruation.
You miscounted cycle days. You can get pregnant if you miscounted cycle days and accidentally had unprotected PIV sex near ovulation. To determine day one of your menstrual cycle, start counting at the first day of red blood, rather than at the end of your menstrual period, says Dr. Sundheimer. “The duration of bleeding for a period also varies, so when you’re counting time to ovulation, it’s better to count from the first day of a period rather than days since bleeding stops.” This can prevent you from having sex too close to ovulation, which can lead to pregnancy.
Your period lasts a long time. It’s not uncommon to have spotting in the day or so before your period starts, and for a few days thereafter. Because of this bleeding, you might falsely believe you’re still on your period and can’t get pregnant. In reality, though, ovulation can be closer than you think.
Managing Fertility After Your Period
You don’t want to worry about getting pregnant before you’re ready. That’s why it’s important to know your cycle and your body, and use protection whenever there’s a chance you could get pregnant. If you had unprotected PIV sex during your period and are concerned that you may be expecting, look out for early pregnancy symptoms like mild lower abdominal cramping, breast tenderness, and moodiness. Other common pregnancy symptoms will manifest closer to six or seven weeks’ gestation, and they include nausea, vomiting and fatigue.