What is fertility/subfertility?
Fertility is the ability to establish a pregnancy within 12 months of having regular unprotected sexual intercourse. Therefore subfertility is defined as involuntary absence of conception within 12 months of trying to conceive (TTC).
A chemical pregnancy means that a sperm has fertilised an egg and the resulting embryo has started to produce a hormone called beta human chorionic gonadotrophin or bHCG – this is the hormone that is tested for on urine pregnancy tests.
Age and Fertility – What do the numbers say?
It is natural that in a modern society with good access to contraception, paired with increased need for economic security that couples are often trying to conceive for the first time at later ages. It is well known fact however that fertility, in both men and women, decreases with age.
At Rylon Clinic we try to champion the idea that knowledge is power with regards to your own fertility, so we have evidenced based knowledge in this page to help you understand your fertility.
In general, a woman’s fertility peaks during the mid-20s. After this there is a natural and gradual decline in successful pregnancy rates. Fertility can be difficult to measure accurately due to individual behavioural variations. For example, how often couples are having sex and whether they are using contraception.
During each menstrual cycle a woman who is under 30 will usually have a 20% chance of successful pregnancy, this drops to 5% chance of successful pregnancy per cycle for a 40-year old woman.
There is also a drop in the success rates of IVF with age in patients using their own eggs. If patients are using donor eggs from young patients, then the rate of success does not drop significantly with the age factor.
Below is a graph summarising success rates of different fertility treatments by age, as well as actual annual conception rates for 2020 in the UK from the office of national statistics. This explains how many women within that age group became pregnant in 2020, it includes all women within the age groups.
Rates of pregnancy with different fertility treatments by age
12 cycles of artificial insemination
computer simulation of fertility
IVF success with own eggs
IVF with eggs from young donors
Actual annual conception rates UK
Why does fertility decline with age?
The reason for this decline in fertility is multifactorial. Women are born with all the egg cells they will ever have; this number slowly decreases throughout life.
When women start their first menstrual period they will have around 500,000 egg cells. If only one egg was released per cycle they would last over 40,000 years. However, during each menstrual cycle many egg cells get stimulated but usually only one of many is released- the other egg cells that were stimulated but not released would resolve naturally and are no longer usable in future cycles.
If many egg cells are released at the same time this can result in multiple births of twins or triplets. Due to this monthly reduction in ovarian egg reserves, by the age of 37 women will have approximately 25,000 eggs remaining, reducing to around 1,000 by menopause.
This differs to men. After puberty the testes will continuously produce sperm cells for
the whole of a man’s life. However, the quality of a man’s sperm also deteriorates with age and advanced age of male partner has been linked to increased miscarriage and congenital anomalies, however paternal age has a less significant effect than maternal age, however there is ongoing research to establish this fact to the full certainty.
Ovarian Reserve Test (ORT)
As discussed above there is a steady decline in ovarian reserve from puberty until menopause.
Ovarian reserve is a measure of a woman’s remaining pool of eggs. There are several investigations that can give an indication of ovarian reserve, but none are perfect. ORT has been used to predict success of potential IVF treatment. In patients with subfertility not planning IVF or with un-tested fertility, the role of ovarian reserve tests is unclear. Some examples of ovarian reserve tests are as follows:
Follicle stimulating hormone (FSH) - A blood test measured on day 3 of the menstrual cycle.
As the name suggests this hormone stimulates ovarian follicles. Follicles contain immature egg cells and need to be stimulated in order to mature and eventually release an egg for fertilisation. In a premenopausal woman, once the ovarian follicles have been stimulated by FSH then the body no longer needs to produce the hormone and so the levels in the blood do not rise greatly. If the levels are greatly increased, it can demonstrate a reduced reserve. It is a relatively inexpensive and non-invasive test, but its usefulness is limited in women with irregular cycle.
Anti-Mullerian Hormone (AMH) – blood test measured on any day of the menstrual cycle
This hormone is produced by follicles in the ovary in their early stages of development before they reach 2-6mm diameter. The level of AMH is strongly correlated to the amount of these early follicles that occur in each cycle, which in turn is related to the number of follicles remaining in the ovary that have not yet started this early stage of development. It is useful in predicting future fertility and also if someone will respond to ovarian stimulation before egg collection as part of IVF treatment. Low levels of AMH are associated with lower success of IVF.
Ultrasound
A transvaginal ultrasound can also assess the number of follicles in each ovary as well as assess the uterus and ovaries for any structural contributors to subfertility. Follicle count can be used to predict how well a patient will respond to IVF in conjunction with other tests. Ultrasound is also a useful diagnostic tool. It is used to identify all the structures in the pelvis such as uterus, abnormal fallopian tubes, and ovaries. When performed by an experienced clinician it can pick up conditions affecting fertility such as fibroids, polyps, hydrosalpinx, endometriosis, ovarian cysts, polycystic ovaries and anatomical anomalies such as uterine septum (a band of tissue within the uterus that can cause difficulties with implantation). In addition to this there is a scan that can be done in conjunction with injecting fluid through the cervix which can test the tubes to make sure they are not blocked. All of these will be discussed in greater detail in our other blogs. It is recommended for the ultrasound to be performed by highly experienced clinicians to ensure accurate results- at Rylon Clinic we offer ultrasound scans from a highly experienced consultant who is skilful in ultrasound scanning with experience in infertility, oncology and general gynaecology. When scans are performed patients can receive the results in real time as the scan is being performed, and ultrasound has no risks and no exposure to radiation.
We offer all these fertility investigations at Rylon clinic in central London. Patients are welcome to choose our clinic to select to book any of these services.
Conditions arising with age
After the age of 35 there is a steep decline in a woman’s fertility, this is partly due to ovarian reserve as discussed above but can also be due to gynaecological conditions arising later in life such as fibroids, endometriosis and endometrial polyps. Fibroids for example (non-cancerous muscular growths in the uterus that can impact fertility) can increase in number and size with age. The chance of being diagnosed with fibroids increases until menopause then sharply declines as fibroids usually shrink once the body stops producing as much oestrogen post-menopause. The frequency of endometrial polyps also increases with time, peaking around 37-45 years old.
Endometriosis is a condition that can affect women throughout their reproductive life and can worsen over time. All of these have an impact on fertility and can often be diagnosed on an ultrasound scan, they will be discussed in more detail in our other upcoming blogs.
Fertility Awareness
The delay in conception is multifactorial, as a result this delay is not always intentional but can lead to lower rates of fertility. One important factor that can influence when patients decide to try to conceive is awareness about the general decline in fertility with age. A robust evidence of several studies showed that amongst those of reproductive age, there is a low to moderate awareness of age-related infertility, with patients in the study generally overestimating the age factor, as well as overestimating how easy it is to become pregnant. It is important therefore, for couples to be aware of their fertility potential and what factors that can affect it, so to help them making an informed choice about the right time to try to for a pregnancy.
Am I fertile?
Without a doubt the best way to see if you can conceive is to start having regular unprotected sex, as no other test of fertility will be perfectly accurate. We know that in general 85% of couples who try to conceive will achieve a pregnancy within one year. The chance of this can be affected by many factors as discussed above and other conditions that we will cover in our other blogs. If you have tried to conceive without success, or if you are not at the stage in your life where you want to conceive but you would like to have more information about your reproductive health, then there are some tests that can be performed at Rylon Clinic for you such as ultrasound scans and blood tests that can certainly give you more information about your fertility.
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