Infertility is something none of us want to consider, but sadly it is becoming more and more prevalent in today’s society. If you have been trying for longer than a year to fall pregnant you might want to ask your OB/GYN for a basic check-up.
The WHO defines infertility as follows:
Infertility is the inability to conceive a child. A couple may be considered infertile if, after two years of regular sexual intercourse, without contraception, the woman has not become pregnant (and there is no other reason, such as breastfeeding or postpartum amenorrhoea). Primary infertility is infertility in a couple who have never had a child. Secondary infertility is failure to conceive following a previous pregnancy. Infertility may be caused by infection in the man or woman, but often there is no obvious underlying cause.
Prevalence of infertility varies depending on the definition, i.e. on the time span involved in the failure to conceive.
- Some estimates suggest that worldwide “between three and seven per cent of all couples or women have an unresolved problem of infertility.
- Many more couples, however, experience involuntary childlessness for at least one year: estimates range from 12% to 28%.
- Fertility problems affect one in seven couples in the UK. Most couples (about 84 out of every 100) who have regular sexual intercourse (that is, every 2 to 3 days) and who do not use contraception will get pregnant within a year.
- About 92 out of 100 couples who are trying to get pregnant do so within 2 years.
- Women become less fertile as they get older. For women aged 35, about 94 out of every 100 who have regular unprotected sexual intercourse will get pregnant after 3 years of trying. For women aged 38, however, only 77 out of every 100 will do so. The effect of age upon men’s fertility is less clear.
- In people going forward for IVF in the UK, roughly half of fertility problems with a diagnosed cause are due to problems with the man, and about half due to problems with the woman. However, about one in five cases of infertility has no clear diagnosed cause.
- In Britain, male factor infertility accounts for 25% of infertile couples, while 25% remain unexplained. 50% are female causes with 25% being due to anovulation and 25% tubal problems/other.
- In Sweden, approximately 10% of couples wanting children are infertile. In approximately one third of these cases the man is the factor, in one third the woman is the factor, and in the remaining third the infertility is a product of factors on both parts.
What causes infertility?
Causes in either sex.
Factors that can cause male as well as female infertility are:
- Genetic factors
- A Robertsonian translocation in either partner may cause recurrent spontaneous abortions or complete infertility.
- General factors
- Diabetes mellitus, thyroid disorders, adrenal disease
- Hypothalamic-pituitary factors
- The presence of anti-thyroid antibodies is associated with an increased risk of unexplained subfertility with an odds ratio of 1.5 and 95% confidence interval of 1.1–2.0.
- Environmental factors
- Toxins such as glues, volatile organic solvents or silicones, physical agents, chemical dusts, and pesticides. Tobacco smokers are 60% more likely to be infertile than non-smokers.
- German scientists have reported that a virus called Adeno-associated virus might have a role in male infertility, though it is otherwise not harmful. Mutation that alters human DNA adversely can cause infertility, the human body thus preventing the tainted DNA from being passed on.
Female Infertility Causes:
- Hypothalamic-pituitary factors
- Hypothalamic dysfunction
- Ovarian factors
- Polycystic ovary syndrome.
- Anovulation. Female infertility caused by anovulation is called “anovulatory infertility”, as opposed to “ovulatory infertility” in which ovulation is present.
- Diminished ovarian reserve, also see Poor Ovarian Reserve
- Premature menopause
- Luteal dysfunction
- Gonadal dysgenesis (Turner syndrome)
- Ovarian cancer
Tubal (ectopic)/peritoneal factors:
- Endometriosis. Endometriosis can lead to anatomical distortions and adhesions (the fibrous bands that form between tissues and organs following recovery from an injury). However, the link between infertility and endometriosis remains enigmatic when the extent of endometriosis is limited. It has been suggested that endometriotic lesions release factors which are detrimental to gametes or embryos, or, alternatively, endometriosis may more likely develop in women who fail to conceive for other reasons and thus be a secondary phenomenon; for this reason it is preferable to speak of endometriosis-associated infertility in such cases.
- Pelvic adhesions
- Pelvic inflammatory disease (PID, usually due to chlamydia)
- Tubal occlusion
- Tubal dysfunction
- Uterine malformations
- Uterine fibroids (leiomyoma)
- Asherman’s Syndrome
- Cervical stenosis
- Antisperm antibodies
- Non-receptive cervical mucus
- Vaginal obstruction
Male Infertility Causes:
Pre-testicular factors refer to conditions that impede adequate support of the testes and include situations of poor hormonal support and poor general health including:
- Hypogonadotropic hypogonadism due to various causes
- Obesity increases the risk of hypogonadotropic hypogonadism. Animal models indicate that obesity causes leptin insensitivity in the hypothalamus, leading to decreased Kiss1 expression, which, in turn, alters the release of gonadotropin-releasing hormone (GnRH).
- Drugs, alcohol
- Strenuous riding (bicycle riding, horseback riding)
- Medications, including those that affect spermatogenesis such as chemotherapy, anabolic steroids, cimetidine, spironolactone; those that decrease FSH levels such as phenytoin; those that decrease sperm motility such as sulfasalazine and nitrofurantoin
- Genetic abnormalities such as a Robertsonian translocation
- Tobacco smoking
- Male smokers also have approximately 30% higher odds of infertility. There is increasing evidence that the harmful products of tobacco smoking kill sperm cells. Therefore, some governments require manufacturers to put warnings on packets. Smoking tobacco increases intake of cadmium, because the tobacco plant absorbs the metal. Cadmium, being chemically similar to zinc, may replace zinc in the DNA polymerase, which plays a critical role in sperm production. Zinc replaced by cadmium in DNA polymerase can be particularly damaging to the testes.
Testicular factors refer to conditions where the testes produce semen of low quantity and/or poor quality despite adequate hormonal support and include:
- Genetic defects on the Y chromosome
- Y chromosome microdeletions
- Abnormal set of chromosomes
- Klinefelter syndrome
- Neoplasm, e.g. seminoma
- Idiopathic failure
- Varicocele (14% in one study)
- Testicular cancer
- Defects in USP26 in some cases
- Acrosomal defects affecting egg penetration
- Idiopathic oligospermia – unexplained sperm deficiencies account for 30 % of male infertility.
- Radiation therapy to a testis decreases its function, but infertility can efficiently be avoided by avoiding radiation to both testes.
Post-testicular factors decrease male fertility due to conditions that affect the male genital system after testicular sperm production and include defects of the genital tract as well as problems in ejaculation:
- Vas deferens obstruction
- Lack of Vas deferens, often related to genetic markers for Cystic Fibrosis
- Infection, e.g. prostatitis
- Retrograde ejaculation
- Ejaculatory duct obstruction