When is your fertile window?

You might be surprised to learn it’s only possible to get pregnant on a small number of days in your cycle. It’s called the ‘fertile window’ and the fertile window starts around 10 days into your cycle, lasting for five days plus the day when you are ovulating.  

If you’re hoping to conceive as soon as possible, here’s what our fertility experts want you to know about your fertile window, including tips on tracking your cycle and the best time to have sex to increase the chances of pregnancy.   

This article covers: 

• What your fertile window is 

• Ways to track when you are ovulating 

• How accurate are ovulation trackers?  

• Tips for conceiving during your fertile window 

How do you track your ovulation and fertile days? 

Calculating your fertile window can be tricky. While ovulation often occurs around day 15 of a typical cycle, about 1 in 2 women experience cycle lengths that vary by five days or more. So, if you’re wondering when you ovulate or when you’re most fertile, simply counting days (the calendar method) may not be accurate unless your cycle is very regular.

Fortunately, there are several ways to track when you're ovulating and identify your most fertile days. If you're trying to conceive, it's important to choose methods that predict ovulation in advance, rather than just confirming that it’s already happened. 

Ovulation tracking methods include: 

• Ovulation prediction kits (OPK) – a digital or manual dipstick that detects a surge of luteinising hormone (LH) in the urine to predict ovulation 

• Cervical mucus – manually checking your discharge to look for signs that ovulation is about to take place 

• Ovulation tracking apps – These use your cycle data to estimate when you’re ovulating, though they are less reliable for irregular cycles.

• Basal body temperature – monitoring the body temperature to look for a small rise, which indicates that ovulation has occurred 

• Progesterone kits – monitoring a rise of progesterone in the blood or urine to confirm that ovulation has taken place 

If you want to predict when you’ll ovulate ahead of time, OPKs and the cervical mucus method are your best bets. Apps can also help estimate your fertile days, but they’re generally less accurate due to natural cycle variability.

Ovulation prediction kits (OPKs) 

OPKs are easy-to-use home tests that help predict when you’re ovulating. They work by detecting a surge in LH in your urine—a signal that your body is about to release an egg.

The LH surge usually occurs about 24 hours before ovulation. For the best results, test at the same time each day (typically between 10am and 2pm), starting around day 10 of your cycle. A positive test indicates that you’re entering your most fertile days, ideal timing for intercourse if you're trying to conceive.

OPKs may not be suitable if: 

• You have PCOS – people with PCOS tend to have naturally high levels of LH, and so an OPK can give a false positive result 
   

• You have very irregular cycles – pinpointing when you ovulate can be difficult and expensive with frequent testing. Consult your doctor for advice. Using OPKs can become expensive due to challenges in finding your ovulation day  

The cervical mucus method  

Checking your cervical mucus is a natural and cost-free way to track your fertile window. Throughout your cycle, the texture and appearance of your discharge changes.

Throughout your menstrual cycle, the consistency of your cervical mucus changes. As your body gets ready to ovulate, your discharge becomes clear, slippery, and wetter. This helps sperm swim into the cervix to reach the fallopian tubes.  

When you’re outside your fertile window, your cervical mucus is likely to be thicker, yellow or white, and may feel more like a paste.  

To check your cervical mucus, insert a clean finger inside the vagina and scoop out some of the discharge. If it’s clear and slippery, you’re likely to be in your fertile window. If it’s very wet and stretches between your fingers, you may be ovulating.  

How can you improve your chances of getting pregnant during your fertile window?

On average, your chances of getting pregnant range from 1 in 10 at the start of your fertile window, to up to 1 in 3 on the day of ovulation, according to widely quoted studies.  
 
The main way to increase your chances of pregnancy is to have unprotected sex at least a couple of times during your fertile window, with semen entering the vagina. But beyond the basics, what else can you do? 

• Consider having regular sex throughout your cycle – no matter which method you use, ovulation prediction isn’t always accurate, so the safest bet may be to have sex every 2 to 3 days throughout the cycle (excluding menstruation) 

• Quit smoking and reduce alcohol intake – a healthy lifestyle helps optimal sperm and egg production, and making these changes can offer a relatively fast boost to your fertility  

• Don’t abstain from ejaculation – there’s no need to ‘save up’ your sperm because ejaculating at least every few days is recommended to flush out dead sperm cells (up to a maximum of once a day) 

• Set realistic goals – couples can feel the pressure when it comes to having frequent sex around ovulation, and it’s better to have an achievable plan rather than feeling stressed and burnt out by an agenda that doesn’t suit your sex drive 
   

• Use whichever position you prefer – the fluid that comes out of the vagina after sex is mostly just semen because healthy sperm quickly swims into the cervix, so most experts would advise that no special position is required for pregnancy 
   

• Consider a fertility assessment – if you’ve been trying for over a year, are over the age of 35, or have very irregular periods, it’s recommended to see a fertility specialist to find out whether you might need extra help conceiving  

Learn more about ways to naturally increase your fertility at home, using simple lifestyle changes to help support healthy egg and sperm production.