Infertility primarily refers to the biological inability of a man or a woman 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
Infertility primarily refers to the biological inability of a man or a woman 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. 
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.
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.
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.
A couple that has tried unsuccessfully to have a child for a year or more is said to be subfertile. 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.
In Britain, male factor infertility accounts for 25% of infertile couples, whilst 25% remain unexplained. 50% are female causes with 25% being due to anovulation and 25% tubal problems/other 
In Sweden, approximately 10% of couples 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.
This section deals with unintentional causes of sterility. For more information about surgical techniques for preventing procreation, see sterilization.
Primary vs. secondary
Couples with primary infertility have never been able to conceive, while, on the other hand, secondary infertility is difficulty conceiving after already having conceived and carried a normal pregnancy. Technically, secondary infertility is not present if there has been a change of partners.
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.
Causes in either sex
Factors that can cause male as well as female infertility are:
- 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
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.
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.
- Main article: Assisted reproductive technology
Treatment of infertility usually starts with medication. In vitro fertilization (IVF) in addition to various forms and developments of it (ICSI, ZIFT, GIFT) is another solution. They all include that the fertilization takes place outside the body. On the other hand, an insemination can make a fertilization inside the body. Other techniques are e.g. tuboplasty, assisted hatching and PGD.
There are several ethical issues associated with infertility and its treatment.
- High-cost treatments are out of financial reach for some couples.
- Debate over whether health insurance companies should be forced to cover infertility treatment.
- Allocation of medical resources that could be used elsewhere
- The legal status of embryos fertilized in vitro and not transferred in vivo. (See also Beginning of pregnancy controversy).
- Anti-abortion opposition to the destruction of embryos not transferred in vivo.
- IVF and other fertility treatments have resulted in an increase in multiple births, provoking ethical analysis because of the link between multiple pregnancies, premature birth, and a host of health problems.
- Religious leaders' opinions on fertility treatments.
- Infertility caused by DNA defects on the Y chromosome is passed on from father to son. If natural selection is the primary error correction mechanism that prevents random mutations on the Y chromosome, then fertility treatments for men with abnormal sperm (in particular ICSI) only defer the underlying problem to the next male generation.
Infertility may have profound psychological effects. Partners may become more anxious to conceive, ironically increasing sexual dysfunction. Marital discord often develops in infertile couples, especially when they are under pressure to make medical decisions. Women trying to conceive often have clinical depression rates similar to women who have heart disease or cancer. Even couples undertaking IVF face considerable stress. 
In many cultures, inability to conceive bears a stigma. In closed social groups, a degree of rejection (or a sense of being rejected by the couple) may cause considerable anxiety and disappointment. Some respond by actively avoiding the issue altogether; middle-class men are the most likely to respond in this way .
There are legal ramifications as well. Infertility has begun to gain more exposure to legal domains. An estimated 4 million workers in the U.S. used the Family and Medical Leave Act (FMLA) in 2004 to care for a child, parent or spouse, or because of their own personal illness. Many treatments for infertility, including diagnostic tests, surgery and therapy for depression, can qualify one for FMLA leave.
- Infertility in science fiction
- Advanced maternal age
- ^ Makar RS, Toth TL (2002). "The evaluation of infertility". Am. J. Clin. Pathol. 117 Suppl: S95–103. PMID 14569805.
- ^ Core clinical cases in Obs and Gynae, 2nd edition, Page 152, published by Hodder Arnold 2006
- ^ [http://sahlgrenska.se/upload/SU/omrade_oss/reproduktionsmedicin/Spermadonatorinformation.pdf Sahlgrenska University Hospital. (translated from the Swedish sentence: "Cirka 10% av alla par har problem med ofrivillig barnlöshet."
- ^ MedlinePlus Medical Encyclopedia: Infertility. Retrieved on 2007-11-21.
- ^ Domar AD, Zuttermeister PC, Friedman R. The psychological impact of infertility: a comparison with patients with other medical conditions. J Psychosom Obstet Gynaecol. 1993;14 Suppl:45-52. PMID 8142988.
- Download a Free Guide to infertility - UK Regulator
- "'Infertility time bomb' warning" at BBC News
- CBC Digital Archives - Fighting Female Infertility
- InterNational Council on Infertility Information Dissemination