When to have sex to get pregnant

By Juliana Kassianos, Transformational Fertility Coach, Yoga Teacher and Founder of The School of Fertility

There’s a saying "timing is everything in life", which is especially true when it comes to making a baby. There’s only a short window of opportunity to conceive each month, so it’s really important to know which days to target.


Your fertile window are the six days when you’re most fertile during your menstrual cycle. They are the five days leading up to ovulation, before your egg is released from your ovary and then the day you ovulate. Why five days before? Because this is the amount of time sperm can potentially survive if the conditions are right. Your egg, however, only survives for up to 24 hours. 

Fertile window: the six days when you're most fertile in your cycle

Fertile window: the six days when you're most fertile in your cycle


To give you an idea of when your fertile window is, you can:

  • Use an online ovulation calculator (or App)

  • Track your hormones

  • Look for changes in your cervical mucus

  • Look out for Mittelschmerz (ovulation pain)

  • Track your basal body temperature


Your fertile window depends on the length of your menstrual cycle. You can work it out by using an online ovulation calculator. This will give you a good idea of when you might ovulate. Be aware that it may not be completely accurate though, as you could ovulate earlier or later than predicted, even if your cycle is regular. Therefore, it’s best to have sex throughout your cycle two to three times a week, but to try daily or at least every other day during the time you believe to be your fertile window, including a few days leeway either side of it.

To be more accurate in pinpointing when your fertile window is, allowing you to make sex more targeted, whilst helping you become more in tune with your body, try taking into account some of the following biomarkers as well: tracking your hormones, looking out for changes in your cervical mucus, looking out for Mittelschmertz and tracking your basal body temperature.


Ovulation Predictor Kits (OPKs) can help you clearly identify when your fertile window is and when you’re going to ovulate by tracking your hormones. There's a Clearblue test, which tells you high fertility days, which are the days leading up to when you ovulate, detected by a rise in your oestrogen levels. Then peak fertility days, which tells you 24-36 hours before you ovulate, detected by a surge in your Luteinising Hormone (LH) levels. This means that you can aim to have sex daily or at least every other day when the high fertility days show. Then when peak fertility shows, you can aim to have sex on that day and the day after.

Some tests only detect a surge in LH, which is not always easy to catch and if you do detect it, it doesn't tell you when the LH surge began. This is why it’s important not to have sex only when you’re ovulating, but to have it in the lead up to ovulation to maximise your chances of conceiving. This is in addition to the fact that sperm stored in the testis for tool long can accumulate DNA damage.


Another indication that your ovulating is to look for changes in your cervical mucus. Around the time of ovulation, it becomes clear, slippery and stretchy, like raw egg whites. If you see this consistency, you’re likely to be either ovulating or just about to, so this is definitely the time to be having sex.


Another perhaps less reliable sign of ovulation is Mittelschmerz, which is German for pain in the middle of the month. It's a one-sided pain in the lower abdomen some women experience around the time of ovulation. The pain is felt like a dull ache or sharp and sudden twinge, that can last for a few minutes, or a day or two. It's not known exactly why it happens, but is thought to be because of the egg being released by the ovary.


To know once you’ve ovulated (i.e. when you can stop having scheduled baby-making sex), you can record your basal body temperature with a special thermometer you can buy from a chemist. Take your temperature every morning as soon as you wake up (before you do anything else) and record the reading on the thermometer. Your basal body temperature will rise after ovulation by up to one degree and stay elevated until your next period. If you don’t get pregnant that month, it will give you an indication of when you might ovulate the following month.


Juliana Kassianos