1 February 2019

When does fertility begin to decrease and how to protect your fertility?

By the Editorial Comitee IVI Blog

The best-known and most obvious cause of declining female fertility is age, with women’s peak fertility age being during their 20s, and quite a steep decline follows after the age of 35. However there are other causes which can accelerate or exacerbate the natural process of declining fertility. Among these are injuries to the fallopian tubes, endometriosis, polycystic ovaries and anovulation, which can occur for a variety of reasons. In this article we explore the issues around age and fertility: the bare statistics relating to the likelihood of becoming pregnant at different ages and what this can mean in individual cases. We also consider the other reproductive problems that can have a bearing on declining female fertility and what help is available. We also show how it is now possible to protect your fertility with the straightforward technique of vitrification of oocytes.


What are the facts, figures and statistics relating to declining female fertility?

Baby girls are born with a fixed number of immature eggs in their ovaries, and this number decreases as they get older. Most girls have around 2 million eggs at birth and this number has already declined to around 400,000 by puberty. At the age of 37 about 25,000 eggs remain and by 51, when most women reach menopause, about 1,000 immature eggs are left but these are not fertile. So by and large, even though most of the eggs a woman is born with will never mature, fertility does depend on the store of eggs remaining. The quality of the eggs also declines as a woman get older.

From an 85% likelihood of becoming pregnant in the early 20s, the percentage falls fairly uniformly to 63% at age 30, down to about 52% at age 35 and then declines more steeply to around 30% at age 40. So from a purely biological and statistical point of view, it’s best to start a family before the age of 35. However, few people’s lives are run with complete efficiency on the basis of the biologically optimum timetable, and the fact is that for social and cultural reasons many women and couples delay their attempts to start a family until later than the biologically ideal time.

Over 80% of couples trying to start a family manage to do so within a year and of those who do not, about half will be successful in the second year of trying, so perseverance can pay off. Even so, because of the narrowing window of time available for help if needed, generally women over the age of 35 are advised to seek some advice and help if necessary after six months. Younger women can ask for advice after one year.


How can you protect your fertility?

Given the catch 22 that while fertility declines as the years pass by, so many of us choose for perfectly sound reasons to delay starting a family until we are well into our thirties, what is to be done? An increasingly utilised solution is for younger women to take the precaution of preserving their eggs until the time is right. This is also invaluable for women who are about to undergo cancer treatment. You can read more about this aspect of fertility preservation in our blog article: Can pregnancy be an option after cancer? Let’s look at what is involved in fertility preservation.

The vitrification of oocytes allows mature eggs obtained following ovarian stimulation to be cryopreserved so that they can be used at a later time, when the patient decides she is ready, with the same prognosis as at the point when they were vitrified. Because in this technique ice crystals do not form, oocyte survival rates are high, allowing fertilisation to be postponed with a reasonable chance of success.

We at IVI use the Cryotop technique. Of the different vitrification techniques that are available, this is the newest and has the best results. IVI has pioneered the incorporation of this technique and we are the European leader in its clinical use. With the Cryotop method, survival figures of up to 97% have been achieved for younger patients (up to 35 years old), with pregnancy rates of 65% and implantation rates of 40%. You can learn more about what’s involved with our video about the vitrification of oocytes on IVI’s YouTube channel.


What are the other causes of declining female fertility and what help is available?

Apart from the inevitable reduction as a result of fertility age, the most common causes of female infertility are fallopian tube injury, endometriosis, polycystic ovaries and anovulation. Treatment and help are available in many cases, naturally depending on the history and individual circumstances of each situation.


Fallopian tube injury

In around 25% of cases of female infertility, the cause is an abnormality affecting the fallopian tubes. In normal conditions, the tubes pick up the ovum that has been released during ovulation, transport the sperm towards the ovum and then guide the fertilised egg to the uterus. Partial damage to the tubes due to an adhesion, or complete damage from a tubal obstruction, prevents this transport and as a result fertilisation will not take place. Tubal damage can occur as a result of infections rising from the cervix or uterus which can result in Pelvic Inflammatory Disease, or PID. The pathogens most frequently involved are those relating to Gonorrhoea, Chlamydia and other STDs.



Endometriosis does not necessarily lead to infertility, but there is a strong association between the two: around 10% of women have the condition, but of infertile women, around 35% have it. The name is derived from the endometrium, the tissue that lines the uterus and which is shed with each monthly cycle.

Endometriosis refers to the phenomenon of this tissue becoming lodged in places other than the uterus. Most commonly this is in the ovaries, fallopian tubes and the lining of the pelvic cavity. The tissue is sensitive to menstrual hormonal changes, giving rise to symptoms of pain during menstruation and sometimes also leading to gastrointestinal and urinary problems. Resulting infertility can occur from changes in the pelvic anatomy leading to obstruction of the tubes or the formation of ovarian cysts.

There are medical and surgical treatments available, including IVF where other techniques have failed, and in many cases becoming pregnant can hinder the progress of the disease.

Polycystic ovaries

Around 20% of women have polycystic ovaries (PCO). The name refers to an increase in the number of small cysts that are observable on the ovary surface with an ultrasound scan. Many women with PCO have no problems with ovulation or getting pregnant but some also have Polycystic Ovarian Syndrome which can lead to irregular menstrual cycles or even the complete absence of menstruation because affected women are not ovulating. With treatment, most women with PCOS are able to get pregnant.

Anovulation: why does it happen?                            

Approximately 35% of women experience anovulation at some time during their lives and often the situation resolves itself. There are several possible causes. Among them are stress, significant weight gain or loss, excessive production of prolactin (the hormone responsible for producing breast milk) and polycystic ovaries.


Finding out more about IVI

If you have any personal concerns about age and fertility and would like to find out more, do browse our website where you can find articles about the latest techniques and treatments, plus all of the up-to-date facts and figures about our way of working and resulting success rates. We publish our independently audited clinical results so that you can judge our record for yourself.

You can also find out more about what to expect from your first visit to IVI. We are very happy to discuss your individual situation when you feel ready to contact us and make an appointment. Phone us on 08 000 850 035 from the UK, or on +34 960 451 185 from other countries, or use our online contact form and we will be in touch.

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