Fertility and egg reserve

Fertility and egg reserve – Definition

Fertility refers to the ability to reproduce.

The egg reserve is the number of eggs in the ovaries. Unlike sperm, eggs are not replenished over the course of a woman’s life – every woman is born with a specific number of eggs, which steadily decreases from the moment of birth. Once most of the eggs have been used up, the menopause begins. From this point onwards, pregnancy is practically impossible. Consequently, how long a woman remains fertile and able to conceive depends largely on her personal egg reserve.

The fertile days are the period during which the chances of becoming pregnant are highest. Normally, a woman has around six fertile days per cycle. These are determined by the menstrual cycle and occur in the days around ovulation. During ovulation, the unfertilised egg is released from the ovary, from where it then travels into the fallopian tube. Ovulation takes place around the middle of the cycle and can vary from cycle to cycle.

Determining ovulation and fertile days

The timing of ovulation is linked to the monthly cycle. On average, a cycle lasts 28 days, although for some women it may be significantly shorter (e.g. 25 days) or longer (e.g. 30 days). If the cycle varies, it is not always easy to determine the fertile days; at the same time, couples who have been trying to conceive for some time should be aware of the woman’s fertile days in order to know when the chances of pregnancy are highest.

There are various methods for determining fertile days. For example, fertile days can be identified using a home ovulation test. For ovulation to occur regularly, the various hormones must work together effectively. The ovulation test detects changes in the fertility hormones LH (luteinising hormone) and oestrogen, thereby making it possible to pinpoint the fertile days accurately.

Other methods for determining fertile days include the so-called calendar method, in which women must accurately record the length of their cycles over several months, and the temperature method, in which basal body temperature must be measured every morning before getting out of bed. There are also other options, although these – like the calendar and temperature methods – are considered less accurate than determining fertile days using an ovulation test.

Furthermore, ovulation and any potential ovulation disorders – which may, amongst other things, be responsible for a couple’s inability to conceive or for a woman’s failure to become pregnant – can be investigated through a blood test and an ultrasound scan.

For many women who have been trying to conceive for some time, pregnancy finally occurs once they know exactly when their fertile days are. On the other hand, there are an increasing number of couples for whom the desire to have a child simply remains unfulfilled, despite identifying ovulation and fertile days.

Worldwide, an increasing number of couples are affected by infertility. The reasons for this may lie with the woman, the man or both partners. You can read more about fertility here.

One possible reason for infertility – and one that is becoming increasingly common these days – is reduced fertility in women due to age.

Reduced fertility in women due to age

It is no longer uncommon for women to wish to have children after the age of 35. The average age of women at the birth of their first child has risen steadily in recent years. According to Statistics Austria, women in Austria were on average 24 years old when they gave birth to their first child in 1985. By way of comparison: in 2013, the average age at first childbirth had already risen to 29. In 1985, 2.3 per cent of first-time mothers were aged between 33 and 36; by 2012, the proportion of 33- to 36-year-olds giving birth for the first time had risen significantly to 11.7 per cent.

There are many reasons for delaying having children. On the one hand, divorce rates are higher today than they were a few years ago, and many people only meet their ideal partner at a ‘more mature’ age. On the other hand, career opportunities and career planning are also playing an increasingly important role in family planning. Other couples, in turn, deliberately postpone having a child until a later stage in order to be able to offer their child greater financial security. Furthermore, there are many other reasons why both women and men choose to wait longer before starting a family.

What is often overlooked in such considerations, however, is that fertility in women declines sharply from a certain age onwards. By the age of 35, a woman is already only about half as fertile as she was at 25. By the age of 40, the chances of pregnancy are significantly lower still. The fact that the likelihood of conception decreases as a woman gets older is linked to her egg reserve, or rather to the loss of eggs and the biological age of the eggs: up until the menopause, women continuously lose hundreds of thousands of eggs. At birth, women have around two million^* eggs stored in their ovaries. By the time of puberty, this number drops to around 400,000 to 500,000^*, and after the onset of the first period, around 500 to 1,000^* eggs are lost per cycle. Furthermore, the age of the eggs is a key factor – for example, in a 30-year-old woman, around 40 to 50 per cent of the eggs are still genetically sound, whereas in a 40-year-old woman, this figure drops to only around ten to 20 per cent.

Assessing the egg reserve

When considering the question of ‘whether there is still enough time to get pregnant’, it may be worthwhile to have your egg reserve assessed. Whilst age is a helpful factor in family planning, it does not always reflect a woman’s actual ‘reproductive age’ – in other words, a 38-year-old may still be very fertile, whilst another woman may already have very low chances of becoming pregnant at the age of 32.

There are several ways to assess egg reserve, including measuring the concentration of anti-Müllerian hormone (AMH), measuring follicle-stimulating hormone (FSH) levels, and the antral follicle count (AFC).

Measuring AMH levels

Anti-Müllerian hormone can be used to provide an indication of an individual’s egg reserve. Each maturing egg is surrounded by a layer of cells known as granulosa cells. The granulosa cells produce anti-Müllerian hormone, which can be detected in the blood. The concentration of anti-Müllerian hormone corresponds to the number of follicles still present and consequently decreases with age.

The hormone is measured in blood serum. If the AMH level is below 1 ng/ml, this is considered an indication of diminished ovarian reserve. It should be noted that the reference ranges vary between the different test systems available and that there are no standardised reference values, which is why the correct interpretation of the AMH level is not always straightforward.

Assessing egg reserve using an ovulation test can be an important aid in decision-making when planning a family, as the result indicates how many more years a woman is likely to be able to conceive and how her individual chances of pregnancy are likely to develop over the years. The egg reserve is assessed by a doctor; however, there are now also tests that can be carried out at home with online analysis. It is always advisable to discuss the results with a specialist in gynaecology and obstetrics or at an IVF centre.

Measuring FSH levels

Follicle-stimulating hormone is a hormone produced in the pituitary gland and is very important for fertility, as it promotes, amongst other things, the maturation of the follicle in the ovary. As a woman ages, her egg reserve decreases due to the gradual depletion of the follicles – the more the follicles are depleted, the higher the FSH concentration at the start of the month. The FSH level can be measured in the blood at the start of the cycle (on the third day of the cycle).

Ultrasound scan

Another way of assessing ovarian reserve is to count the number of antral follicles using ultrasound at the start of the menstrual cycle. During the ultrasound scan, the follicles in the ovaries are measured and counted. If the scan reveals seven or fewer antral follicles, fertility is likely to be significantly reduced.

What factors influence fertility?

Inability to conceive or reduced fertility can have various causes in both women and men.

Possible causes in women include, in addition to ‘advanced’ age, conditions such as thyroid disorders (hyperthyroidism and hypothyroidism), malformations of the fallopian tubes, ovaries and/or the uterus, endometriosis, polycystic ovary syndrome (PCOS), infectious diseases (e.g. chlamydia), being underweight or overweight, as well as certain underlying medical conditions and their treatment.

Possible causes in men include, amongst others, reduced sperm quality (OAT syndrome), testosterone deficiency and other hormonal imbalances, circulatory disorders, erectile dysfunction, underdevelopment or congenital malformations or injuries to the testicles, inflammation of the prostate and urethra, being underweight or overweight, as well as certain underlying medical conditions and their treatment.

Furthermore, certain lifestyle factors can have a significant impact on fertility in both women and men.

Fertility and lifestyle

The fertility of both women and men is influenced by many factors, including lifestyle factors such as smoking, alcohol and stress. Certain lifestyle changes can increase the chances of conception and a complication-free pregnancy.

Diet and weight: A varied and nutrient-rich diet is not only important for health, but can also have a positive effect on fertility. A regular intake of various nutrients, including, for example, folic acid, omega-3 fatty acids, zinc, selenium, B-complex vitamins, and vitamins C and E, in sufficient quantities can improve fertility and help bring you one step closer to having a baby.

Furthermore, a healthy and balanced diet has a positive effect on body weight. Severely overweight women often suffer from menstrual irregularities due to a hormonal imbalance. Studies have shown that a body mass index (BMI) of over 27 kg/m² significantly reduces the likelihood of pregnancy. In men, being overweight can have a negative impact on testicular function and sperm production.

Smoking: Due to the harmful effects of the various substances in cigarettes, smoking has a detrimental effect on fertility in both women and men and also reduces the chances of success of any fertility treatment. Studies show that AMH levels are significantly lower in women who smoke daily than in non-smokers. As smoking exerts its negative effects even before pregnancy begins, the common intention of many women and men to give up smoking once they become pregnant comes too late. Anyone wishing to improve their fertility and increase their chances of having a child should give up smoking as soon as possible.

Alcohol: An occasional glass of wine is unlikely to affect fertility. Moderate alcohol consumption (around seven alcoholic drinks per week), however, can have a negative impact on fertility. Although it is not entirely clear exactly how alcohol affects fertility, there is some evidence to suggest that alcohol influences, amongst other things, the maturation and ovulation of the egg, as well as sperm quality.

^*Figures vary in the literature