Introduction

There are many reasons why a woman may miss her usual monthly period, or why periods might stop altogether.

Most women have a period every 28 days or so, but it's common to have a slightly shorter or longer cycle than this (from 24 to 35 days).

Some women don't always have a regular menstrual cycle. Their period may be early or late, and how long it lastsand how heavy it is may vary each time.

The most common reasons are:

• pregnancy
• stress
• sudden weight loss
• being overweight or obese
• extreme overexercising
• taking thecontraceptive pill
• reaching themenopause
• polycystic ovary syndrome (PCOS)

Periods can alsosometimes stop as a result of a long-termmedical condition, such asheart disease, uncontrolled diabetes, anoveractive thyroid,or premature ovarian failure.

Pregnancy

You might be pregnant if you're sexually active and yourperiod is late. Pregnancyis a common reason why periodsunexpectedly stop. It can sometimes happen if thecontraception you're usingfails.

It might be that your period is simply late, so you could waita few days to see if it arrives. If it doesn't arrive, you can do a pregnancy testto confirm whether or not you're pregnant.

It's important to be aware that you can get pregnant in the days after your period is normally due. This can happen ifthe release of an egg (ovulation) is delayedfor example, as a result of illness or stress.

Stress

If you're stressed, your menstrual cycle can become longer or shorter, your periods may stop altogether, or they might become more painful.

Try to avoid becoming stressed by making sure you havetime to relax. Regular exercise, suchas running, swimming and yoga, can help you relax. Breathing exercises can also help.

If you're finding it hard to cope withstress, cognitive behavioural therapy (CBT)may be recommended. CBT is a talking therapy that can help you manage your problems by changing the way you think and act.

Sudden weight loss

Excessive or sudden weight loss can cause your periods to stop. Severely restricting the amount of calories you eat stops the production of hormones needed for ovulation.

Your GPmay refer you to a dietitian if you're underweight, whereyou have abody mass index (BMI) of less than 18.5. The dietitian will be able to advise you about how to regain weight safely.

If your weight loss is caused by aneating disorder, such as anorexia, you'll be referred to a psychiatrist.

Being overweight or obese

Being overweight or obese can also affect your menstrual cycle. If you're overweight, your body may produce an excess amount of oestrogen, one of the hormones that regulate the reproductive system in women.

The excessoestrogen can affect how often you have periods, and can alsocause your periods to stop.

Your GPmay refer youto a dietitian if you'reoverweight or obese, witha BMI of 30 or more, and it's affecting your periods. The dietitian will be able to advise you aboutlosing weight safely.

Extreme overexercising

The stress that intense physical activity places on your body can affect the hormones responsible for your periods. Losing too much body fat through intense exercise can also stop you ovulating.

You'll be advised to reduce your level of activity if excessive exercise has caused your periods to stop.

If you're a professional athlete, youmay benefit from seeing a doctor who specialises in sports medicine. They'll be able to give you advice about how to maintain yourperformance without disrupting your periods.

Contraceptive pill

You might miss a period every so often if you're taking the contraceptive pill. This isn't usually a cause for concern.

Some types of contraception, such as theprogestogen-only pill, contraceptive injection and intrauterine system (IUS), particularly Mirena, can cause periods to stop altogether.

However, your periods should return when youstop using these types of contraception.

Menopause

You may start missing periods as you approach the menopause. This is because oestrogen levels will start to decrease, andovulation will become less regular.After the menopause, your periods will stop completely.

The menopause is a natural part of the ageing process in women, which usually occurs between the ages of 45 and 55. The average age for a woman to reach the menopause is 51in the UK.

However, around1 in 100 women experience the menopause before the age of 40. This is known as premature menopause or premature ovarian failure.

Polycystic ovary syndrome (PCOS)

Polycystic ovariescontain a large number of harmless follicles, which are underdevelopedsacs inwhich eggs develop. If you have PCOS, thesesacs are often unable to release an egg, which means ovulation doesn't take place.

PCOS is thought to be very common, affecting about1 in every 10 women in the UK.The condition is responsible for as many asone in three cases of stopped periods.

When to see your GP

See your GP if you're not pregnant you've had a negative pregnancy testand you've missed more than three periods in a row.

If you're sexually active and you haven't taken a pregnancy test, your GP may advise you to take one.

They may also ask you about:

• your medical history
• your family's medical history
• your sexual history
• any emotional issues you're having
• any recent changes in yourbody weight
• the amount of exercise you do

Your GPmay recommend waiting to see whether your periods return on their own. In some cases you mayneedtreatment for your periods to return.

You should also see your GP if your periods stop before you're 45 or you're still bleeding when you're over 55.

Referral to a specialist

If your GP thinks an underlying medical condition might have caused your periods to stop, they may refer you to a specialist.

Depending on what your GP suspects is causing the problem, you may be referred to:

• a gynaecologist aspecialist in treating conditions that affect the female reproductive system
• an endocrinologist a specialist in treating hormonal conditions

You may have a full gynaecological examination and various tests, including:

• blood tests toseewhether you have abnormal levels of certain hormones, such as prolactin, thyroid-stimulating hormone, follicle-stimulating hormone, or luteinising hormone
• an ultrasound scan,CT scan orMRI scan to identify any problems with your reproductive system or the pituitary gland in your brain

Treating underlying conditions

Iftest results indicate an underlying medical condition has caused your periods to stop, you may be offeredtreatmentfor yourcondition.

For example, if the cause is PCOS,you may be advised totake the contraceptive pill or tablets containing a hormone called progesterone.

Hormone medication is usually recommended. Treatments to try include the contraceptive pill or hormone replacement therapy (HRT).

Read aboutJohanna's experience of premature ovarian failure.

If you have an overactive thyroid gland, you may begiven medication to stop your thyroid gland producing too many hormones.

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