Fertility guide: When can you get pregnant after your period?

Understanding your menstrual cycle

It might be an unwanted visitor each month, but if you're trying to conceive (or trying not to!) it's worth getting to know the ins and outs of your menstrual cycle and understanding at which point you're most likely to be fertile each month.

In a nutshell, the menstrual cycle is the term used to describe the time between the first day of a woman's period to the day before her next period starts. The number of days of the cycle differs from one woman to the next, but the average is around 28 days, which is why people talk about it being the "time of the month".

Menstrual cycles in the region of 21 days to 35 days in length are considered to be within the "normal" range. If your cycle is shorter or longer than this and you have any concerns you should speak to your doctor.

The menstrual cycle is made up of four different phases: menstruation (your period), the follicular phase, ovulation and the luteal phase, although as most of these phases occur without any signs or symptoms it can be hard to know which phase you're in.

The whole cycle is controlled by hormones. In the first half of the cycle, shortly after your period has finished, rising levels of the hormone oestrogen trigger the ovary to mature and release an egg. This is called ovulation and is the golden window of opportunity for getting pregnant each month. Oestrogen also causes the womb lining to start to thicken in anticipation of a fertilised egg to implant.

In the second half of the cycle, the egg travels down the fallopian tubes and the hormone progesterone readies the womb for implantation of a developing embryo. If the egg has been fertilised by a sperm, the egg is reabsorbed into the body and as the levels of progesterone and oestrogen fall the womb lining comes away and leaves the body in the form of a period, which lasts between 2 and 7 days. Depending on the length of your cycle the time between the release of the egg from the ovary to your next period is between 10 - 16 days.

When do you ovulate?

"Most people ovulate two weeks before they start their period, so for example, if you have a regular 28-day cycle you will ovulate around day 14," says Dr Amin Gorgy, fertility consultant and co-director of The Fertility & Gynaecology Academy in London. The process of ovulation lasts around 12 to 24 hours before the released egg will die if not fertilised by a sperm.

However, if you have a particularly short cycle, all the phases of the cycle will be much shorter and closer together and therefore ovulation may occur only days after your period finishes. "Sperm will live in the reproductive tract for up to five days", says Dr Gorgy, so in some cases where women ovulate early or have long periods and have unprotected sex straight after their period finishes, they may successfully conceive.

Women with a naturally short cycle could ovulate as early as six days after the first day of their period, which means that although not very common, it is possible to get pregnant in the days after your period ends.

Signs of ovulation

Some women experience obvious signs and symptoms that they are ovulating, while others will feel nothing at all. However, both are completely normal and just depend on your own body. Signs of ovulation that you may be able to notice and track include a 0.2-0.6°C rise in your basal body temperature (the lowest temperature your body reaches when at rest) just after you ovulate.

Your temperature may also dip slightly just before you ovulate. These temperature changes happen due to changing levels of the hormones such as oestrogen and progesterone throughout your menstrual cycle.

Another sign of ovulation that you can track and use to identify your fertile days is a change in your cervical mucus. Just after your period ends you'll have little or no discharge. This will then change to sticky white mucus before becoming more thin and watery like egg white at the time of ovulation.

Around the time you're ovulating, you may also notice some breast tenderness, appetite and mood changes, mild lower abdominal pain, changes to the shape and feel of your cervix, light spotting, a heightened sense of smell and taste, increased libido and bloating.

How to identify your fertile days

The best way to identify your fertile window to find out whether you have a short cycle and are more likely to ovulate soon after your period ends is by tracking your cycle for three months using a calendar or online tracker. This will allow you to count the average number of days of your full cycle for a few months.

While you're tracking the number of days, you can then keep an eye out for the signs and symptoms of ovulation mentioned above simply by taking more notice of your body around day 14 of your cycle or by using over-the-counter ovulation predictor kits or fertility monitors.

How to avoid pregnancy

You can also track your menstrual cycle to avoid getting pregnant by only having sex on your least fertile days. However, it's important to know that natural family planning in this way isn't 100% effective¹ (when followed correctly this method is between 91 - 99% effective) and having unprotected sex does not stop you from getting or passing on sexually transmitted diseases.

To use the fertility awareness method to avoid pregnancy every day you need to record your body temperature and the details of your vaginal mucus plus track the length of your menstrual cycle each month. Tracking these will allow you to predict your most fertile days and avoid having sex or using a condom on these days.

When to seek medical advice

If you've been monitoring your menstrual cycle to predict ovulation either in an attempt to get pregnant or to avoid it and you think something may be wrong, such as an extremely short or long cycle then you should speak to your doctor.

You might also want to seek medical advice if you've been having unprotected sex for a year or more and still haven't conceived. If you are over 35 then you can speak to your doctor after 6 months of trying to conceive and if you're over 38 you can seek medical advice after 3 months of trying.

References:

^{1. Natural family planning, NHS Online}

Read more:

• Ovulation symptoms: 10 signs of ovulation to know
• What is early menopause and how can it affect fertility?
• Can vitamin D supplements help me get pregnant?