Age and fertility: what does the science really say?

The loss of ovarian reserve with age

A 2004 study of 782 couples having regular unprotected sexual intercourse found that the estimated percentage of infertility was 8% for women aged 19 to 26, 13–14% for women aged 27 to 34, and 18% for women aged 35 to 39 [1].

The biological basis of this decline in fertility with increasing age in women appears to stem from several factors: 

• a woman's germ cells (reproductive cells) are not renewed during her lifetime,
• the decline and use of follicles leads to a reduction in the number of oocytes from birth to the menopause
• the quality of existing oocytes declines with age [2].
   

The reduction in the number of follicles containing eggs in the ovaries is known as "ovarian reserve loss". Women begin to lose their ovarian reserve before becoming infertile and before their periods become irregular. 

Although it is not possible to act on the ovarian reserve, it is nonetheless possible to support the quality of oocytes. A boost female fertility, with coenzyme Q10 for example (at least 200mg) may help. 

Fertility loss begins well before the menopause. As women are born with their entire stock of follicles, the reserve of resting follicles is gradually depleted. 
 

As the ovarian reserve declines, follicles become less and less responsive to stimulation by FSH (follicle-stimulating hormone, essential for ovarian development), meaning they require greater stimulation for an egg to mature and ovulate [3]. 

What does the scientific evidence say about age and fertility?
 

75% of women who begin trying to conceive naturally at age 30 will achieve a conception resulting in a live birth within the following year. These figures decline progressively, falling to 66% at age 35 and then to 44% at age 40 [4].

Compared with women aged 20 to 24, fertility is reduced by 31% in women aged 35 to 39 [5].

What should we make of this scientific data?

Numerous scientific studies have evaluated the impact of age on fertility. They consistently demonstrate a decline over the course of a lifetime. 

The figures are an indicator, but they evolve 

The figures differ between studies, due to the fact that not all studies include the same number of women, and that age categories are not always studied in the same way (comparison of ages 20-25 with 30-35 / or directly with age 40). The figures should therefore be interpreted with caution, as the data may evolve. Beyond a certain age, there is no change so drastic that you will inevitably receive a negative pregnancy test. 

There is no drastic change at 35

The age of 35 is set arbitrarily based on studies that classify women by age group, but no drastic change occurs between the ages of 34 and 35. It is an average given by the studies, but every woman is different, and age is an important factor though not the only one at play. In principle, a 35-year-old woman with a healthy lifestyle will have as many if not more chances of conceiving than a 30-year-old woman with poor lifestyle habits. It seems necessary to assess each woman on a case-by-case basis rather than generalising solely on the basis of age.

Not all couples are comparable 

Statistics also vary depending on the couple, namely their frequency of sexual intercourse, the use of non-hormonal contraception as the last method used, and the timing of intercourse. Each of these factors in turn impacts the chances of having a positive pregnancy test, beyond age. In a study taking these three factors into account, they showed that this could increase the probability of conceiving by 6% [8].

Other factors must be taken into account

It is recognised that nutrition also has an impact on fertility, meaning that two women of the same age with different lifestyles will in principle not have the same chances of becoming pregnant. 

These figures should not frighten you, as stress is also a very important factor in fertility. It has been shown that the more stressed a woman is, the less likely she is to conceive. Yet the older we get, the more we worry about our "biological clock", which means that stress compounds the effect of age in reducing the chances of becoming pregnant. 

Don't forget: less likely does not mean impossible!

The pool of follicles from which oocytes develop is complete at birth. It will not increase over the course of a woman's life and will gradually diminish until it is exhausted at the menopause. This decline in follicle reserve is accompanied by a deterioration in oocyte quality.

Women have a lower chance of becoming pregnant and a higher chance of miscarriage due to the decline in egg quality as the number of remaining eggs decreases. This also affects the foetus, as a decline in oocyte quality can lead to chromosomal abnormalities. 

These changes tend to become most apparent when a woman reaches her mid- to late thirties [9]. 

Screening for trisomy can be carried out using a maternal blood test from 9 weeks of pregnancy and an ultrasound scan at 12 weeks. If a risk is detected, free foetal DNA tests can be performed. 

An amniocentesis may also be performed. However, this procedure is not without risk and can lead to a risk of miscarriage. It appears that the benefit/risk ratio between detecting the risk of a genetic abnormality and the risk of inducing a miscarriage justifies performing an amniocentesis at the age of 35.
 

Note: Statistics from studies on the risk of having a child with trisomy 21 vary and are not all interpreted in the same way. Higher figures are observed when results take into account the detection of trisomy by amniocentesis. Indeed, this procedure is carried out early in pregnancy, and it is known that a chromosomal abnormality is often a factor in early miscarriages; therefore, the actual figures for the risk of giving birth to a child with trisomy may be lower than those found in studies. 
 

Finally, treatments will be offered to women considered to have an "advanced maternal age". They may receive aspirin to reduce the risk of pre-eclampsia, have additional ultrasound scans, and undergo tests to monitor the baby's condition. These tests are carried out from the age of 35, thereby distinguishing a 34-year-old woman from a 40-year-old woman, even though no such clear threshold exists between the ages of 34 and 35. It is necessary to carry out these tests and/or treatments on an individual basis, according to each woman's profile, rather than simply on the basis of an age limit.

In France in 2015, 3.1% of children were born as a result of assisted reproductive technology. 

Assisted reproductive technology from the age of 35 

The study from the Centre d'Etude et de Conservation des Oeufs et du Sperme (CECOS), conducted on women who had undergone donor insemination, indicated that the fertility declined significantly with age from the age of 30 [20]. Overall, the study shows a slight but significant decline after 30 and a marked decline after 35. The probability of success with insemination over 12 cycles was 73% in women under 31, falling to 61% for those aged 31–35 and further to 54% for those over 35.
 

In another study, they showed that assisted reproductive technology did not compensate for the decline in fertility. If a woman delays her pregnancy attempt by 5 years, that is from age 30 to 35, her chances of conceiving will be reduced by 9% and treatment will only improve the outcome by 4%. If she delays from age 35 to 40, her chances will be further reduced by 25% and treatment will account for only 7%. In other words, assisted reproductive techniques compensate for only half of the births lost by delaying a pregnancy attempt from age 30 to 35, and less than 30% of the births lost by delaying from age 35 to 40 [21].

Assisted reproductive technology beyond the age of 40

In women over 40, the success rate of a assisted reproductive technology journey for superovulation with timed intrauterine insemination (a technique used in cases of infertility) is generally less than 5% per cycle. By comparison, the success rate is approximately 10% in women aged 35 to 40 [22]. 

IVF is more effective but also has relatively low success rates in women aged 40 and over, generally less than 20% per cycle. At 43, the chances of becoming pregnant via IVF are below 5%, and by 45 the chances become virtually nil [23].

Many factors beyond age can impact fertility: lifestyle, diet, smoking, stress, lack of sleep, and so on. 

To find out more about how to get pregnant of course, do check out our article on the subject. 

Nutrition is a factor we can act on directly. Many nutrients are beneficial for fertility, such as magnesium and omega-3s, which play a role in hormonal balance — essential for fertility. While some things are beyond our control, we can see our diet as an important key to our feminine health, a way to take back power. 
 

For example, in a study in rats, they showed that dietary omega-3 fatty acids (with 2.1% of total calories provided by DHA) allowed them to reproduce well beyond the expected age for these animals, and that this also led to a remarkable improvement in egg quality [24]. They believe this result can be extrapolated to women, and that DHA consumption could help improve the age-related decline in fertility. 

Baby Bump is our pregnancy food supplement which covers over 100% of requirements for all B-group vitamins, 500% of vitamin D3, nearly 100% of vitamin K and 200% of vitamin B9 in methylated form. It also covers 50% of daily zinc requirements and 133% of iodine intake. It also contains DHA and choline. A real boost for your fertility.
 

To find out more about nutrition and fertility, do check out our article on the subject.

To help you boost your fertility, we have developed Ovo+. Based on Coenzyme Q10, NAC and tryptophan to support egg quality and boost fertility. 

Because fertility is 50/50, the male fertility food supplement in powder form Cocooning+ men will help boost male fertility. Based on 3 active ingredients (CoEnzyme Q10, carnitine and N-acetyl-cysteine), it helps improve sperm quality, motility and concentration. It is also recommended to carry out a male fertility test, in order to take a comprehensive approach. 

Studies consistently show a decline in fertility from the age of 30–35. This is explained by a reduction in the number of eggs as well as a deterioration in their quality, resulting in a lower probability of becoming pregnant, but also an increased risk of pregnancy-related complications (genetic abnormalities, miscarriages, etc.). 
 

Precise figures are difficult to establish as studies are not all conducted in the same way and examine women from different age groups. However, they all reach the same conclusion: the older we get, the more fertility declines. 
 

This does not mean that after the age of 35 you will no longer be able to have a baby! These studies should not frighten you or lead you to think that you will not become pregnant — they simply show that it may become more challenging due to the natural ageing of reproductive function. 
 

If you are experiencing fertility problems, women under 35 who have been trying to conceive for 12 months or more are advised to seek medical advice, as are women over 35 who have been trying to conceive for 6 months or more.