When is the best time to get pregnant?

When's the best time to have sex to conceive?

The most effective time to have sex is during your fertile window, which can last up to six days every month. These six days are the five days leading up to, and the day of, ovulation (Lynch et al 2006, NCCWCH 2013), when your body releases an egg.

Your egg will survive for 12 to 24 hours once released (NHS 2014). But sperm can survive for up to a week (NCCWCH 2013). So there's a six-day window for sperm to meet an egg.

You're most likely to conceive if you have sex one or two days before you ovulate (Lynch et al 2006, Germano and Jennings 2006, NCCWCH 2013). But it's tricky to pinpoint the exact day or two just before ovulation. So if you don't want your sex life to be ruled by the calendar, your best bet is simply to enjoy sex every two or three days.

If you want to be more precise, though, you will need to work out when you will ovulate. When you'll ovulate in any given cycle depends on:

• the length of your menstrual cycle
• how regular your periods are

A menstrual cycle can be as short as 22 days or as long as 36 days (Fehring et al 2006). On average, a woman gets her period about 14 days after she's ovulated (ACOG 2015).

If you have a 28-day menstrual cycle, you're likely to ovulate around the middle of your cycle. If you have a short cycle, you could ovulate within days of your period ending. A long cycle could mean that you won't ovulate until two weeks after your period has ended.

Nearly half of women have a cycle length that varies by more than seven days (Fehring et al 2006). If your menstrual cycle is different from one month to the next, your fertile window may also vary by about a week between each period.

That's why it's best to have sex every two to three days throughout your cycle (NCCWCH 2013). It's more effective than focusing your efforts only on the days you think you're about to ovulate. Also, sex every two to three days improves the quality of sperm compared to daily sex (NCCWCH 2013).

How do I know when I'm about to ovulate?

You may be very aware of when you ovulate, or you may not notice any changes at all. If you're thinking about getting pregnant, get in touch with your body. Signs that you're approaching ovulation can start around three weeks before you expect your next period. Try looking out for:

• Increased vaginal discharge that's wetter, and like stretchy egg white. This is called fertile mucus (Alliende et al 2005, Bigelow et al 2004, Campbell and Rockett 2006, Scarpa et al 2006).
• Slight discomfort on one side of your belly (mittelschmerz) (Campbell and Rockett 2006).
• Feeling more sexy (Pillsworth et al 2004, Wilcox et al 2004).

One of the simplest ways of working out your fertile days is to check your cervical mucus every day (Germano and Jennings 2006, IRH 2009). Changes to your mucus are one of the easiest things for you to spot.

Do irregular periods make it harder to get pregnant?

Irregular periods don't necessarily mean that you're less fertile than women with regular periods. But if your periods are irregular or are more than 36 days apart, it's worth seeing your GP.

Sometimes, irregular cycles are caused by conditions such as polycystic ovarian syndrome (PCOS) or a thyroid disorder. These conditions could affect your chances of conceiving, so it's better to get help sooner rather than later (NCCWCH 2013).

The more irregular your periods are, the more difficult it can be to work out when you're fertile. So practise looking for changes in fertile mucus by checking daily (Germano and Jennings 2006, IRH 2009). Try to have sex when you notice two or more days of wet, slippery mucus. Or you may find it easier to just have regular sex throughout your cycle.

To find out more about your fertile window, try our ovulation calculator. And read our article for helpful tips for spotting other signs of ovulation.