Subfertility is defined as when a couple fail to conceive within 18 months of having regular unprotected intercourse. 85% of couples will conceive naturally within 1 year. Of 100 couples trying to conceive naturally:

  • 20 will conceive within 1 month
  • 70 will conceive within 6 months
  • 85 will conceive within 1 year
  • 92 will conceive within 2 years.

If a couple have never conceived, it is known as primary subfertility. Secondary subfertility is when a couple have had one or more babies in the past, but are having difficulty conceiving again.

Some women get pregnant very quickly but for others it can take longer. Although there is not a cut off point to say when a couple is subfertile, it is best to seek advice if you have not conceived after one year of trying. As fertility decreases with increasing age, women over the age of 35 or  younger women with factors that are known to affect fertility should seek advice sooner. Subfertility may be caused by many different factors and in approximately 30% of couples a cause cannot be identified. In these cases, sub fertility is classified as ‘unexplained’.

Subfertility in Women

Ovulation disorders
Subfertility is most commonly caused by problems with ovulation (the release of an egg from the ovaries). In some women, eggs will never be released and in others ovulation may occur on an infrequent basis. Ovulation problems can occur as a result of a number of conditions that are outlined below:

  • Premature ovarian failure – when the ovaries stop working before the age of 40
  • Polycystic ovarian syndrome (PCOS) – a condition which makes it more difficult for the ovaries to produce an egg
  • Thyroid problems – both an overactive and an underactive thyroid gland can affect ovulation
  • Chronic conditions – if you have a debilitating condition such as a cancer or AIDS, it can prevent your ovaries from releasing eggs.

Womb and Fallopian Tubes
The fallopian tubes pick up eggs from the ovary. The fertilised egg (embryo) then passes down the tube to the womb (uterus) where it implants in the lining of the womb (endometrium). If the womb or fallopian tubes become damaged, then it may be very difficult to conceive naturally. This can occur following a number of procedures or conditions as outlined below:

  • Pelvic surgery – this can sometimes cause damage and scarring of the fallopian tubes.
  • Cervical surgery – this can sometimes cause scarring or damage to the cervix.
  • Sub mucosal fibroids – these are benign (non-cancerous) tumours that can develop in the muscle underneath the lining of the womb and may reduce the chance of an embryo implanting.
  • Endometriosis – this is a condition where cells normally found in the womb lining start to grow outside the uterus. This can cause adhesions in the pelvis and limit the movement and function of the fallopian tubes. Endometriosis can also affect the ovaries and impair the production and release of eggs.
  • Previous sterilisation – some women choose to be sterilised if they do not wish to have any more children. Sterilisation involves blocking the fallopian tubes and the process is rarely reversible. Surgery can be performed in some cases to attempt to reverse this.

Medicines and Drugs
The side effects of some types of medication and drugs can affect your fertility. These medicines include:

Non-steroidal anti-inflammatory drugs (NSAIDs)
Long-term use or high dosage use of NSAIDs like Ibuprofen or Naproxen can make it more difficult to conceive.

Chemotherapy
The medicines used with chemotherapy can sometimes cause ovarian failure which means that the ovaries may no longer be able to function properly and produce eggs. Ovarian failure can be permanent.

Illegal Drugs
Drugs such as marijuana and cocaine can seriously affect your fertility making it more difficult to ovulate. They may also adversely affect the functioning of the fallopian tubes.

Age
Subfertility in women is closely linked to age. Women in their 20s are about twice as fertile as women in their late 30s. The biggest decrease in fertility begins during the mid-thirties.

Subfertility in Men

Semen
The most common cause of male sub fertility is abnormal semen (the fluid ejaculated during sex that contains sperm). Abnormal semen accounts for 75% of male sub fertility cases and the cause of abnormal semen is often unknown. Semen can be abnormal for a number of reasons which are listed below:

  • Decreased number of sperm – the sperm count may be very low or there may be no sperm at all
  • Decreased sperm motility – if the motility of the sperm is decreased it will be harder for the sperm to swim to the egg
  • Abnormally shaped sperm – sometimes sperm can be an abnormal shape, making it harder for them to move and fertilise an egg. Many cases of abnormal semen are unexplained but there are several factors that can affect semen and sperm.

Testicles
The testicles are responsible for producing and storing sperm. If they are damaged, the quality of sperm can be affected. This may occur in men who have had:

  • An infection of the testicles
  • Testicular cancer
  • Testicular surgery
  • Previous mumps, undescended testicles and CAVD may affect fertility.
  • Occupations in which the testicles can become very hot e.g. long distance lorry drivers

Ejaculation disorders
Some men have a condition which makes it difficult for them to ejaculate. In other cases,  the semen is ejaculated into the bladder (retrograde ejaculation). The ejaculatory ducts can also be blocked or obstructed and this can make it difficult to ejaculate normally.

Some medicines and drugs can affect sperm

  • Sulfasalazine – this is an anti-inflammatory medicine used to treat conditions such as Crohn’s disease (inflammation of the intestine) and rheumatoid arthritis. This medicine can decrease the number of sperm produced. However, its effects are only temporary and sperm production should return to normal when the drug is stopped.
  • Anabolic steroids – these steroids are often used illegally to build muscles and improve athletic performance. Long term use or abuse of anabolic steroids can reduce the sperm count and sperm motility.
  • Chemotherapy – the medicines used with chemotherapy can sometimes severely reduce the production of sperm.

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