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You notice that the tabetic has the power of holding water for an indefinite period. He is also impotent—in fact, two excellent properties to possess for a quiet day on the river.
DR DUNLOP, TEACHING AT CHARING CROSS HOSPITAL, 1913
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Infertility is defined as the absence of conception after a period of 12 months of unprotected sexual intercourse.1 The inability to conceive can be a very distressing and emotional problem for a couple, who need considerable care, empathy and relatively rapid investigation of their problem. In assessing a couple with the problem of subfertility, it is appropriate to involve both partners in the consultation.
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Human fertility depends on a complex series of events, including:2
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production of gametes (sperm and oocytes) capable of fertilisation
release of the oocyte into the fallopian tube after ovulation
the right number of sperm have to be placed in the right place at the right time
implantation and development of the embryo in the hormonally primed uterine mucosa
maintenance of the growing fetus in the uterus until pregnancy is full term
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As a general rule, the major factors limiting fertility are approximately one-third female, one-third male and one-third combined male and female. In addition, there are couples who fulfil the three primary fertility factors (egg, sperm and tubes) but do not conceive. This is known as unexplained (idiopathic) subfertility and accounts for 10–20% of subfertile couples.
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Key facts and checkpoints
Infertility affects about 10–20% (1 in 7) of couples.2
Fertility in women and men declines naturally with age.
After the age of 32, female fertility decreases by 1.5% per year.
Increasing female age is a common cause of decreased fertility.
The main identifiable causes of male infertility are failure of spermatogenesis, failure of sperm delivery, impaired sperm quality and sperm autoimmunity.2
Female factors include ovulation dysfunction, tubal disease, uterine disorders and peritoneal pathology.3
Polycystic ovarian syndrome (PCOS) is the most common cause of ovulatory dysfunction.4
In up to 20% of couples, no apparent cause is identified (idiopathic).2
Assisted reproductive technology (ART) helps the majority of subfertile couples to achieve pregnancy, although success rates reduce with increasing maternal age.5
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PHYSIOLOGICAL FACTORS
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6Fertility in the male requires:
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normal hypothalamic function producing gonadotrophin-releasing hormone (GnRH)
normal pituitary function producing the gonadotrophin hormones—follicle stimulating hormone (FSH) and luteinising hormone (LH)
normal seminiferous tubule and Leydig cell function
normal sperm transport and delivery
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Facts about sperm viability:
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the maximum number of viable sperm is found in the ejaculate after a 48-hour abstinence
after entering receptive cervical mucus, sperm are capable of fertilising an egg for up to 5 to 6 days
sperm survive for less than ...