Ovulation and fertility
What is ovulation?
Ovulation is when an egg is released from one of the ovaries during a menstrual cycle. The egg travels down the fallopian tubes and the womb prepares for implantation of a developing embryo (fertilised egg).
You can only get pregnant if the egg is fertilised by sperm. Occasionally, more than 1 egg is released during ovulation. If more than 1 egg is fertilised you can become pregnant with more than one baby.
If you don’t become pregnant, the egg is reabsorbed into the body and the womb lining comes away and leaves your body as a period. It takes about 10 to 16 days for a period to start after an egg is released.
Ovulation doesn’t happen every month for every woman. There are some conditions that may interfere with ovulation, such as endometriosis and polycystic ovarian syndrome. Try not to worry, but Ii you are not getting a monthly period and are trying to get pregnant, it's a good idea to speak to your doctor.
When am I most likely to get pregnant?
You are at your most fertile from around 7 days before you ovulate until about 2 days afterwards, particularly the day before and the day that you ovulate. This is because sperm can live for around 5 days inside a woman’s body, so if you’ve had sex in the days before ovulation, the sperm can ‘wait’ for the egg to be released. These days before and just after the egg is released is often called the ‘fertile window’.
Your ‘fertile window’
When you’re struggling to get pregnant, finding out about your fertile window may turn into an all-consuming task.
It is also complicated by the fact that some women reach their fertile window earlier or later in their cycle, so it can be difficult to predict when you reach your fertile window, even if you have regular periods.
However, if you have regular, unprotected sex (sex every 2 to 3 days without contraception) you are likely to get pregnant. More than 8 out of 10 couples where the woman is under 40 years old will get pregnant within one year if they have regular, unprotected sex.
Having said that, having sex every second day can be an issue for various reasons, particularly if pregnancy doesn’t happen quickly. Therefore, being aware of your cycle and knowing more about your fertile window can be helpful.
The tips below should help you figure out when you are at your most fertile. Be wary of depending too much on unscientific apps and tools and narrowing sex down to the wrong time each month.
Top tips for finding the fertile window
These are things you can do to track your cycle and find out when you are most fertile.
1. Keep a diary of your menstrual cycle
The menstrual cycle is the time from the first day of a woman’s period to the day before her next period.
Women’s menstrual cycles vary in length. The average is 28 days, although both longer and shorter cycles are normal. It doesn’t matter how long your cycle is, for most women ovulation will usually occur 10 to 16 days before the start of your next menstrual cycle. Check out our ovulation calculator here.
Keeping a record of when your period usually starts and stops will help you find your fertility window.
If you have a regular menstrual cycle you may be able to work out when you’re likely to ovulate but be wary of narrowing it down too much in case you get it wrong.
2. Use an ovulation predictor test kit
There is a hormone (called the luteinizing hormone, LH) that increases in the urine before ovulation. Monitoring this hormone surge has been shown to help pinpoint ovulation and the fertile window.
You can buy ovulation predictor test kits that can detect this hormone in your urine. The tests are available from chemists or supermarkets or online and are simple to use.
Ovulation predictor kits may not be suitable if you have a known fertility issue that affects your menstrual cycle, such as polycystic ovary syndrome (PCOS). This is because this condition affects your hormones, so you may not get an accurate reading. Talk to your GP if you have PCOS and want to get pregnant.
It is best to become familiar with your usual menstrual cycle to help figure out when you should start testing. If you have an irregular cycle then an ovulation predictor kit can still help you identify the time of ovulation, but you may use more of the test sticks. Follow the instructions on the packet to find out more.
There are lots of ovulation predictor testing kits and fertility apps on the market.
3. Look out for breast pain, bloating and mild tummy pain
It’s not a reliable way of predicting ovulation, but some women may have these symptoms when they ovulate so it may help you get to know your cycle.
Some women get a pain in one side of their lower abdomen (stomach area) when they ovulate. The pain can be a dull cramp or a sharp and sudden twinge.
Ovulation pain is often normal, but see your GP if you’re worried or the pain is severe. Sometimes the pain can be caused by medical conditions that may affect your fertility, such as endometriosis or a sexually transmitted infection.
4. Check your cervix
The feel of your cervix changes when you’re close to ovulation. You can check your cervix by putting your clean finger inside you. If it feels high and soft and not low and firm, you may be ovulating.
5. Look out for cervical mucus changes
Vaginal secretions (vaginal discharge) change during your menstrual cycle. If you’re ovulating, your discharge will become thinner and stretchy, a bit like raw egg white.
6. Check your basal body temperature
Use a basal thermometer to take your temperature every morning before you get out of bed and record it on a chart. This should be done before eating or drinking and ideally at the same time every morning. There’s a small rise in temperature (around 0.2C) after you’ve ovulated and until your next period. You will be least likely to be fertile at this point, so you need to chart your temperature for a few months, to see if there's a pattern to your cycle. If there is, you may be able to estimate when you'll next ovulate. There are apps available that help you record and track your temperature and cervical mucus changes.
The instructions around this method are very specific so it is difficult to get right and the results are less likely to be accurate.
7. Keep an eye on your sex drive
Some research has found a link between hormone levels and sexual desire during a menstrual cycle. Plainly speaking, when you ovulate the hormones produced by the ovaries change, making your sex drive go up.
So if you’re feeling particularly sexy, your fertility may be at it’s highest. How convenient!
NHS Choices. Periods and fertility in the menstrual cycle https://www.nhs.uk/conditions/periods/fertility-in-the-menstrual-cycle/ (Page last reviewed: 28/07/2016. Next review due: 28/07/2019)
Clinical Knowledge Summaries (2016) Contraception – natural family planning https://cks.nice.org.uk/contraception-natural-family-planning#!topicSummary
Allen J Wilcox et al (2000) The timing of the “fertile window” in the menstrual cycle: day specific estimates from a prospective stud. British Medical Journal. 2000 Nov 18; 321(7271): 1259–1262.
NHS Choices. Trying to get pregnant. https://www.nhs.uk/conditions/pregnancy-and-baby/getting-pregnant/ (Page last reviewed: 23/01/2018. Next review due: 23/01/2021)
NICE Guideline (2013) Fertility problems: assessment and treatment National Institute for Health and Care Excellence https://www.nice.org.uk/guidance/cg156
Freis A, et al. (2018) Plausibility of menstrual cycle apps claiming to support conception. Frontiers in public health 2018 Apr 3;6:98. doi: 10.3389/fpubh.2018.00098.
NHS Choices. How can I tell when I’m ovulating? https://www.nhs.uk/common-health-questions/womens-health/how-can-i-tell-when-i-am-ovulating/ (Page last reviewed: 18/05/2016. Next review due: 18/05/2019)
Hsiu-Wei, Su et al. (2017) Detection of ovulation, a review of currently available methods. Bioengineering & Translational Medicine 2017 Sep; 2(3): 238–246. Published online 2017 May 16. doi: 10.1002/btm2.10058
Clinical Knowledge Summaries (2018) Infertility https://cks.nice.org.uk/infertility#!topicSummary
NHS Choices. Ovulation pain https://www.nhs.uk/conditions/ovulation-pain/ (Page last reviewed: 26/07/2016 Next review due: 26/07/2019)
NHS Choices. Naturally family planning. Fertility awareness https://www.nhs.uk/conditions/contraception/natural-family-planning/ (Page last reviewed: 22/02/2018. Next review due: 22/02/2021)
Roney JR, Simmons ZL (2013) Hormonal predictors of sexual motivation in natural menstrual cycles. Hormones and behaviour 2013 Apr;63(4):636 doi: 10.1016/j.yhbeh.2013.02.013.