I have irregular cycles – how do I know my fertile days?

Written by:, PhD, Founder and Inventor of the Proov test — the first and only FDA-cleared test to confirm successful ovulation at home.

Irregular cycles are more common than you may think and while they can make it a little more difficult to get pregnant, the good news is that it’s definitely not impossible. There are plenty of tools to help you on your journey — even if you have irregular cycles. 

A question that comes up often for those with irregular cycles is, “How do I find my fertile days?” Well, we’re here to help!

I have irregular cycles – how do I know my fertile days?

Wondering how to find your most fertile days with irregular cycles? We can help!

Why is knowing when I’m fertile important when trying to get pregnant?

In school, we’re often taught that getting pregnant is the easiest thing and it can happen when you’re trying or not. While getting pregnant is that easy for some women, the truth is that a healthy, young fertile couple trying to conceive only has a 25% chance of pregnancy in any given month.

In order for pregnancy to occur and for that pregnancy to reach the second trimester — when risk of miscarriage decreases significantly — several conditions need to be met:

  • A healthy egg
  • A healthy sperm
  • For the egg and the sperm to meet 
  • A healthy embryo
  • A thick, receptive uterine lining
  • Optimal progesterone levels throughout the first trimester (and then through the rest of the pregnancy)

Egg and sperm quality is mostly determined by age — i.e. the older you are, the less genetically normal eggs you likely have. Contrary to a lot of information on the internet, it’s really difficult to influence sperm and egg quality on lifestyle changes alone. 

So even if you lead a generally healthy life — eat a balanced diet, exercise, and try to avoid or diminish stress — there’s one very important aspect you need to consider when trying to conceive: timing.

It might sound silly, but a very large recent study proved that one of the main causes of infertility in young healthy couples is mistiming of intercourse. In other words, people do not have intercourse when they should be to allow for a higher chance of possible pregnancy, during their fertile days.

One of the main causes of mistiming intercourse is assuming you ovulate right on cycle day 14 (with cycle day 1 being the first day of your period). While this is the average ovulation day for women, and is most likely true for women with 28 days cycles, ovulation that results in pregnancy may occur as early as cycle day 8 and as late as cycle day 22.

So, knowing when you’re going to ovulate during your cycle is important. But even then, understanding when to time intercourse around ovulation is equally as critical. 

An egg has a very short life span, between 12 and 24 hours, during which it may get fertilized. When fertilization doesn’t occur, the egg disintegrates and pregnancy is no longer a possibility. So, having intercourse too late after ovulation occurs means you may miss the egg altogether.

Luckily, we know sperm can live up to 5 days in the female reproductive tract, therefore these 4-5 days before the egg is actually released help us cover what is called the  “fertile window.” In order to find out when your fertile window is, of course, you need to be able to estimate ovulation day — something especially tricky for those with irregular cycles. 

So if I have irregular cycles how do I know my fertile days?

Even if your cycles are irregular, you can still be ovulating, it just may be a little more difficult to figure out when exactly it’s happening.

Unfortunately, calendar-based ovulation tracking apps likely aren’t the best option for you. These apps typically use set algorithms to “guess” when ovulation should occur, but don't take into account other things that could be happening in your body. 

For women with irregular cycles, we typically recommend tracking ovulation with your hormones. Reproductive hormones control ovulation and your cycle. Understanding how and when they change can help you understand when ovulation is going to occur. 

Estrogen rises at the beginning of your cycle as the ovary chooses the egg that is going to ovulate. The higher your estrogen levels get as you near the middle of your cycle, the closer you are to ovulation. 

Once estrogen is high enough to signal the egg is ready for ovulation, the brain sends a surge of luteinizing hormone (LH) to the ovary to trigger ovulation. LH tests, also called ovulation tests, track LH levels in your urine.

Most women ovulate 12-36 hours after a first positive ovulation test. That means your best bet is to start having intercourse 3-4 days before a positive ovulation test, and continue having intercourse 2 days after it.

Tracking estrogen (or its urine marker, E1G) alongside LH can help you identify when ovulation should be coming sooner, making it easier to know when it’s time to start having intercourse. 

The Proov Complete kit is a great option for those with irregular cycles as it tracks E1G and LH all from the same test. Additionally, Complete measure PdG (a urine marker of progesterone) that can help you confirm ovulation and closes your fertile window. 

I have irregular cycles – how do I know my fertile days?

Another method, very old and preferred by women with irregular cycles and hormonal imbalances is cervical mucus tracking. As estrogen levels increase, vaginal discharge consistency changes to signal you are entering your most fertile time of the month.  

I’m getting lots of positive ovulation tests. What does that mean?

If you have irregular cycles and receive positive LH tests for many days (or even most of your cycle), we recommend consulting your doctor. This can be a sign of polycystic ovarian syndrome (PCOS).

PCOS is often characterized by a hormonal imbalance that can lead to chronically elevated LH levels. This can cause false positive LH tests that don’t actually result in ovulation. 

For women with PCOS, we typically recommend cervical mucus monitoring in order to detect the rise in estrogen as a marker of oncoming ovulation. Additionally, we recommend confirming ovulation with something like Proov Confirm — a PdG (progesterone marker) test. 

Not only can Proov Confirm help you understand if you ovulated, but it can also help you understand if your ovulation was successful, meaning if PdG production after ovulation allowed for a higher chance of possible pregnancy. 

I have irregular cycles – how do I know my fertile days?

So, while irregular cycles can make it more difficult to tell when you’re fertile, there’s still plenty of tools to help you along your trying to conceive journey. And our team will be there every step of the way!

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