Infertility

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Infertility primarily refers to the biological inability of a person to contribute to conception. Infertility may also refer to the state of a woman who is unable to carry a pregnancy to full term. There are many biological causes of infertility, some which may be bypassed with medical intervention.[1]
Women who are fertile experience a natural period of fertility before and during ovulation, and they are naturally infertile during the rest of the menstrual cycle. Fertility awareness methods are used to discern when these changes occur by tracking changes in cervical mucus or basal body temperature.

Definition
There are strict definitions of infertility used by many doctors. However, there are also similar terms, e.g. subfertility for a more benign condition and fecundity for the natural improbability to conceive. Infertility in a couple can be due to either the woman or the man, not necessarily both.

[edit] Infertility
Reproductive endocrinologists, the doctors specializing in infertility, consider a couple to be infertile if:
the couple has not conceived after 12 months of contraceptive-free intercourse if the female is under the age of 34
the couple has not conceived after 6 months of contraceptive-free intercourse if the female is over the age of 35 (declining egg quality of females over the age of 35 account for the age-based discrepancy as when to seek medical intervention)
the female is incapable of carrying a pregnancy to term.

Subfertility
A couple that has tried unsuccessfully to have a child for a year or more is said to be subfertile meaning less fertile than a typical couple. The couple's fecundability rate is approximately 3-5%. Many of its causes are the same as those of infertility. Such causes could be endometriosis, or polycystic ovarian syndrome.

Primary vs. secondary infertility
Couples with primary infertility have never been able to conceive,[2] while, on the other hand, secondary infertility is difficulty conceiving after already having conceived (and either carried the pregnancy to term, or had a miscarriage). Technically, secondary infertility is not present if there has been a change of partners.

Prevalence
Generally, worldwide it is estimated that one in seven couples have problems conceiving, with the incidence similar in most countries independent of the level of the country's development.
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. [3]
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.[3]
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 have no clear diagnosed cause [4]
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 [5]
In Sweden, approximately 10% of couples are infertile.[6] 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.

Causes
This section deals with unintentional causes of sterility. For more information about surgical techniques for preventing procreation, see sterilization.
Common causes of infertility:
Ovulation problems
tubal blockage
male associated infertility
age-related factors
uterine problems
previous tubal ligation
previous vasectomy
unexplained infertility
Tuberculosis (TB

Virus
German scientists have reported that a virus called Adeno-associated virus might have a role in male infertility[7], though it is otherwise not harmful[8].

Causes in either sex
For a woman to conceive, certain things have to happen: intercourse must take place around the time when an egg is released from her ovary; the systems that produce eggs and sperm have to be working at optimum levels; and her hormones must be balanced.[9]
There are several possible reasons why it may not be happening naturally. In one-third of cases, it can be because of male problems such as low sperm count.Some women are infertile because their ovaries do not mature and release eggs. In this case synthetic FSH by injection or Clomid (Clomiphene citrate) via a pill can be given to stimulate follicles to mature in the ovaries.
Problems affecting women include endometriosis or damage to the fallopian tubes (which may have been caused by infections such as chlamydia).
Other factors that can affect a woman's chances of conceiving include being over- or underweight for her age - female fertility declines sharply after the age of 35. Sometimes it can be a combination of factors, and sometimes a clear cause is never established.
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
Kallmann syndrome
Hyperprolactinemia
Hypopituitarism
Environmental Factors
Toxins such as glues, volatile organic solvents or silicones, physical agents, chemical dusts, and pesticides. [10][11]

Combined infertility
In some cases, both the man and woman may be infertile or sub-fertile, and the couple's infertility arises from the combination of these conditions. In other cases, the cause is suspected to be immunological or genetic; it may be that each partner is independently fertile but the couple cannot conceive together without assistance.

Unexplained infertility
In about 15% of cases the infertility investigation will show no abnormalities. In these cases abnormalities are likely to be present but not detected by current methods. Possible problems could be that the egg is not released at the optimum time for fertilization, that it may not enter the fallopian tube, sperm may not be able to reach the egg, fertilization may fail to occur, transport of the zygote may be disturbed, or implantation fails. It is increasingly recognized that egg quality is of critical importance and women of advanced maternal age have eggs of reduced capacity for normal and successful fertilization.

Assessment
If both partners are young and healthy, and have been trying for a baby for 12 months to two years without success, a visit to the family doctor could help to highlight potential medical problems earlier rather than later. The doctor may also be able to suggest lifestyle changes to increase the chances of conceiving. [12]
Women over the age of 35 should see their family doctor after six months as fertility tests can take some time to complete, and age may affect the treatment options that are open in that case.
A family doctor will take a medical history and give a physical examination. They can also carry out some basic tests on both partners to see if there is an identifiable reason for not having achieved a pregnancy yet. If necessary, they can refer patients to a fertility clinic or a local hospital for more specialized tests. The results of these tests will help determine which is the best fertility treatment.