Skip to Content

Fertile Period: When is My Fertile Window?

By: Author Dr Akatakpo Dunn, MBBS, PG Dip Ultrasound, Prof Dip O&G (RCPI) Medical Director & Lead Obstetrician/Ultrasonologist, Verah Clinic & Maternity

Posted on Last updated:

Fertile window (also called fertile period) is the roughly 6-day part of your menstrual cycle when you are most likely to get pregnant if you have unprotected sex.

If you’re serious about getting pregnant or preventing it, then you must understand your fertile days. This is because intercourse during this time is much more likely to lead to pregnancy (although not 100% guaranteed).

The first step to know your best days to get pregnant is understanding ovulation. If you don’t know when you ovulate, then you should read this guide on ovulation and how to know your fertile mucus.

What is fertile window?

Fertile window is the 6 possible days in your menstrual cycle that you can easily get pregnant. It is usually calculated with lifespan of the egg and sperm. Normal sperm can have a life span of up to about 5 days in cervical mucus and the female reproductive tract, while a normal ovum or egg has a lifespan of about 12–24 hours after ovulation. This means that if you have intercourse up to 5 days before ovulation, you can still get pregnant.

Your fertile window is therefore 5 days before you ovulate and about one day after.

Some terms used to calculate your fertile days

Before we go into how to calculate ovulation and fertile days, let me explain some terms.

LMP (Last menstrual period)

This is the first day of the last time you saw your period. For example, if your period lasted for 5 days and ended on the 15th of March 2014, your LMP is 10th of March 2014.

Menstrual cycle

This is the difference in days between 2 of your period. It is also the difference between 2 of your LMP.

How to calculate your menstrual cycle? If you already know your LMP, then you have to wait for your next period. The difference between your LMP and the next LMP is your menstrual cycle length.

For example, if your LMP is 15th March 2014, and you notice your next period on 14th of April 2014, then your menstrual cycle is about 30 days.

However, the length of your menstrual cycle can be affected by emotional stress, drugs, chronic (long term) illness and academic or work activities.

What’s the normal menstrual cycle? If the length of your cycle is between 21 to 35 days then it’s usually considered normal in adults.

Period or menstruation

This is the cyclical bleeding that comes out of your vagina every month. It is due to hormone changes in your body. Normal period should last between 3 to 7 days.

Read more: Menstrual cycle and menstruation.

Ovulation

This is also a cyclical process during your menstrual cycle where the ovary releases an egg into the fallopian tubes for fertilization. If you do not ovulate, you cannot get pregnant. Cleveland Clinic

When is my fertile window?

You already know your fertile days are within your menstrual cycle. So how can you detect your fertile days?

Your cervical mucus

The first day of your menstrual cycle is the first day of your period. After your period, your vagina becomes dry and then you will notice thick white discharge coming out.

As you get closer to the middle of your menstrual cycle, your thick discharge becomes creamy white or milky white discharge that is sticky and without smell. This type of discharge is not very fertile as it is difficult for sperm to swim through.

Just after your creamy discharge, your discharge becomes stretchy, clear, egg-white and watery. You can easily notice your discharge stretches between your fingers and does not break. This is your ovulation discharge and returns to creamy discharge or thick discharge after ovulation. 

Your fertile cervical mucus that indicates your fertile days are:

Regular intercourse during this type of vaginal discharge can get you pregnant.

Basal body temperature (BBT)

This is another way you can check your fertile window. It gives you clue about when you’re likely to ovulate. Before ovulation, your body temperature is at its baseline. Just before you ovulate, there may be a small dip in your basal body temperature. After ovulation and due to the effect of progesterone, there is usually a slight increase of basal temperature by about 0.5–1.0ºF (0.3–0.6ºC), which stays up until your next period. 

To be able to use your basal temperature, you should monitor your menstrual cycle for months. BBT is your body temperature at rest. It is done early in the morning while you are still on your bed before any activity.

However, it is only very useful after months of regular basal temperature charting and is not a very reliable method on its own to prevent pregnancy.

Ovulation kits and fertility monitors

Ovulation kits are used to predict when ovulation will occur due to surge of luteinizing hormone (LH). During your menstrual cycle, LH surges and reaches its peak about 12 hours before ovulation. A positive test means you’re likely to ovulate soon.

Also, the fertility monitor can predict your fertile days for about 5 days prior to ovulation. Though more expensive, it is a non-invasive way to easily identify your fertile days. These tools work in a similar way to those described in Mayo Clinic guidance on ovulation signs.

Ovulation signs and symptoms

If you understand some of your ovulation signs and symptoms, you can know when you ovulate. Symptoms of ovulation can include:

Some women may also notice bloating, a higher sex drive, or a softer, higher cervix at this time. Tommy’s 

How can I get pregnant in my fertile window?

Now you know how to calculate your fertile days, you can increase your chances of getting pregnant by having regular intercourse every 2 to 3 days throughout your cycle and especially every 1 to 2 days within your fertile period. It is usually easier to get pregnant if you’ve had intercourse in the days just before ovulation.

The most fertile time to get pregnant is the 2 days before ovulation and the day of ovulation, and up to about 24 hours after ovulation. Having intercourse during this time will increase your chances of getting pregnant, as also suggested by Mayo Clinic ovulation guidance.

If you are trying to use your fertile window to avoid pregnancy, remember that fertility awareness methods can have higher failure rates with typical use and must be followed very carefully. The NHS natural family planning page explains this in more detail.

Easy example to make you understand your fertile days

Here is an example to help you understand how to calculate your fertile days easily.

Question

Mrs Beric saw her period on the 14th of March 2015 and currently started seeing her period today, the 13th of April 2015. She has a regular 30 day cycle. When is her fertile window?

Answer

Ovulation, which is the release of egg from the dominant follicle in the ovary, occurs about 14 days before your next period. This is fairly constant in many women, although in real life it can vary by a few days.

Since her menstrual cycle is regular, she should see her next period by 12th or 13th of May.

What is her fertile window?

Now subtract 14 days from 13th of May. You will get 29th or 28th of April. She is expected to ovulate around the 29th of April.

Your fertile window is usually 5 days before ovulation and a day after ovulation. Therefore, between 24th to 29th of April is her fertile days.

Please note:

  • Your cycle may not always be regular. It could be affected by emotions, stress, weight changes, medications and illness.

  • All women do not ovulate at the same time. Some women may experience early ovulation or late ovulation.

  • Most women will start seeing their period about 10 to 16 days after ovulation. This “luteal phase” length is fairly constant for each woman, once you know your pattern.

  • Regular charting of your menstrual cycle to know its length is vital to calculate your fertile period, but it is still only an estimate.

FAQs about fertile period and days

These are some commonly asked questions that may concern you. Do you have a question for me? Let me know. Comment below or send me an email.

What does it mean when a woman is fertile?

A woman is fertile when she has a reasonable chance of getting pregnant after intercourse because an egg can meet sperm. If you have intercourse during your fertile period, you’re more likely to get pregnant, although some couples may still have difficulty because of male or female fertility problems.

What does it mean to be fertile and ovulating?

Being fertile means you can get pregnant. Your fertile days or period is between 5 days prior to ovulation and 1 day after it. Ovulation means that your ovary releases egg into your fallopian tube where fertilization can take place. If you’re fertile and ovulating, then you can easily get pregnant with unprotected sex.

When are you most fertile?

Your fertile window lasts about 6 days: 5 days before and 1 day after ovulation. However, you are most fertile in the 2 days before ovulation and on the day of ovulation.

Can you only get pregnant when you ovulate?

Pregnancy happens when sperm meets an egg. This can only occur around the time of ovulation, but because sperm can live for several days inside your body, you can get pregnant from sex in the days before you actually ovulate. Without ovulation (or medical treatments like IVF), there is no natural way to get pregnant.

What are my fertile days after period or menstruation?

Your fertile days after your period depend on your menstrual cycle length. If your cycle is a regular 28-day cycle, then you are likely to ovulate about 14 days before your next period, which for many women works out to roughly the middle of the cycle. Depending on how long your bleeding lasts, that can be around a week or more after your period ends. Your fertile window is the best time to get pregnant after period.

Can you get pregnant on your fertile days?

Yes. If you have intercourse during your fertile period, you have a high chance of getting pregnant. If you are trying to prevent pregnancy, then you should avoid unprotected intercourse during this period or use a reliable contraceptive method.

What is fertile window symptoms and meaning?

Some of the symptoms of ovulation period are:

  • Cervical mucus change with stretchy, egg-white, watery discharge that does not break when stretched between your fingers.

  • Breast pain.

  • Ovulation cramps or pain.

  • Soft and high cervix in your vagina.

Fertile window vs ovulation: What’s the difference?

Fertile window is 6 days during your menstrual cycle that you can get pregnant, while ovulation is the process when your ovaries release one or multiple eggs into the fallopian tubes. Understanding ovulation and fertile mucus is the first step to get pregnant or prevent it.

Now its your turn. Do you have problems calculating your fertility period after menstruation? Or are you still confused about your ovulation symptoms?

Let us help you. You can use the Medplux fertile days calculator.

If you have been having regular unprotected sex for 12 months (or 6 months if you are 35 years or older) without getting pregnant, please talk to your doctor and read the World Health Organization infertility fact sheet for more information and support.