Infertility
Infertility is the inability to naturally conceive a child or the inability to carry a pregnancy to term. There are many reasons why a couple may not be able to conceive, or may not be able to conceive without medical assistance. (Note: although some aspects of this article may be generalizable, it deals primarily with infertility as pertains to human couples.)
Contents
1 Definition
2 Causes
2.1 Primary vs. secondary
2.2 Female infertility
2.3 Male infertility
2.4 Combined infertility
2.5 Unexplained infertility
3 Treatment
Definition
The International Council on Infertility Information Dissemination (INCIID) considers a couple to be infertile if1:
they have not conceived after a year of unprotected intercourse, or after six months in women over 35;
there is incapability to carry a pregnancy to term.
Healthy couples in their mid-20s having regular sex have a one-in-four chance of getting pregnant in any given month. This is called "fecundity".
Causes
Primary vs. secondary
According to the American Society for Reproductive Medicine, infertility affects about 6.1 million people in the U.S., equivalent to ten percent of the reproductive age population. Female infertility accounts for one third of infertility cases, male infertility for another third, combined male and female infertility for another 15%, and the remainder of cases are "unexplained"2.
A Robertsonian translocation in either partner may cause recurrent abortions or complete infertility.
"Secondary infertility" is difficulty conceiving after already having conceived and carried a normal pregnancy. Apart from various medical conditions (e.g. hormonal), this may come as a result of age and stress felt to provide a sibling for their first child. Technically, secondary infertility is not present if there has been a change of partners.
Female infertility
Factors relating to female infertility are:
General factors
Diabetes mellitus, thyroid disorders, adrenal disease
Significant liver, kidney disease
Psychological factors
Hypothalamic-pituitary factors:
Kallmann syndrome
Hypothalamic dysfunction
Hyperprolactinemia
Hypopituitarism
Ovarian factors
Polycystic ovary syndrome
Anovulation
Diminished ovarian reserve
Luteal dysfunction
Premature menopause
Gonadal dysgenesis (Turner syndrome)
Ovarian neoplasm
Tubal/peritoneal factors
Endometriosis
Pelvic adhesions
Pelvic inflammatory disease (PID, usually due to chlamydia)
Tubal occlusion
Uterine factors
Uterine malformations
Uterine fibroids (leiomyoma)
Asherman's Syndrome
Cervical factors
Cervical stenosis
Antisperm antibodies
Insufficent cervical mucus (for the travel and survival of sperm)
Vaginal factors
Vaginismus
Vaginal obstruction
Genetic factors
Various intersexed conditions, such as androgen insensitivity syndrome
Male infertility
Factors relating to male infertility include3:
Pretesticular causes
Endocrine problems, i.e. diabetes mellitus, thyroid disorders
Hypothalamic disorders, i.e. Kallmann syndrome
Hyperprolactinemia
Hypopituitarism
Hypogonadism due to various causes
Psychological factors
Drugs, alcohol
Testicular factors
Genetic causes, e.g. Klinefelter syndrome
Neoplasm, e.g. seminoma
Idiopathic failure
Cryptorchidism
Varicocele
Trauma
Hydrocele
Mumps
Posttesticular causes
Vas deferens obstruction
Infection, e.g. prostatitis
Retrograde ejaculation
Hypospadias
Impotence
Genetic causes
Some causes of male infertility can be determined by analysis of the ejaculate, which contains the sperm. The analysis includes counting the number of sperm and measuring their motility under a microscope:
Producing few sperm, oligospermia, or no sperm, azoospermia.
A sample of sperm that is normal in number but shows poor motility, or asthenozoospermia.
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.
Treatment
Fertility medication which stimulates the ovaries to "ripen" and release eggs (e.g. clomifene citrate, which stimulates ovulation)
Surgery to restore patency of obstructed fallopian tubes (tuboplasty)
Donor insemination which involves the woman being artificially inseminated with donor sperm.
In vitro fertilisation (IVF) in which eggs are removed from the woman, fertilized and then placed in the woman's uterus, bypassing the fallopian tubes. Variations on IVF include:
Use of donor eggs and/or sperm in IVF. This happens when a couple's eggs and/or sperm are unusable, or to avoid passing on a genetic disease.
Intracytoplasmic sperm injection (ICSI) in which a single sperm is injected directly into an egg; the fertilized egg is then placed in the woman's uterus as in IVF.
Zygote intrafallopian transfer (ZIFT) in which eggs are removed from the woman, fertilized and then placed in the woman's fallopian tubes rather than the uterus.
Gamete intrafallopian transfer (GIFT) in which eggs are removed from the woman, and placed in one of the fallopian tubes, along with the man's sperm. This allows fertilization to take place inside the woman's body.
Other assisted reproductive technology (ART):
Assisted hatching
Fertility preservation
Freezing (cryopreservation) of sperm, eggs, & reproductive tissue
Frozen embryo transfer (FET)
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