|
Page: Causes
Main article
| Home > Pregnancy and Birth > Causes |
This section deals with unintentional causes of sterility. For more information about surgical techniques for preventing procreation, see sterilization.
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".
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.
Some women are infertile because their ovaries do not mature and release eggs. In this case synthetic FSH can be given as injections to stimulate eggs to mature in the ovaries.
Female infertility
Factors relating to female infertility are:
* General factors
o Diabetes mellitus, thyroid disorders, adrenal disease
o Significant liver, kidney disease
o Thrombophilia
* Hypothalamic-pituitary factors:
o Kallmann syndrome
o Hypothalamic dysfunction
o Hyperprolactinemia
o Hypopituitarism
* Ovarian factors
o Polycystic ovarian syndrome
o Anovulation
o Diminished ovarian reserve
o Luteal dysfunction
o Premature menopause
o Gonadal dysgenesis (Turner syndrome)
o Ovarian neoplasm
* Tubal/peritoneal factors
o Endometriosis
o Pelvic adhesions
o Pelvic inflammatory disease (PID, usually due to chlamydia)
o Tubal occlusion
o Tubal dysfunction
* Uterine factors
o Uterine malformations
o Uterine fibroids (leiomyoma)
o Asherman's Syndrome
* Cervical factors
o Cervical stenosis
o Antisperm antibodies
o Insufficient cervical mucus (for the travel and survival of sperm)
* Vaginal factors
o Vaginismus
o Vaginal obstruction
* Genetic factors
o Various intersexed conditions, such as androgen insensitivity syndrome
Male infertility
Factors relating to male infertility include:
* Pretesticular causes
o Endocrine problems, i.e. diabetes mellitus, thyroid disorders
o Hypothalamic disorders, i.e. Kallmann syndrome
o Hyperprolactinemia
o Hypopituitarism
o Hypogonadism due to various causes
o Drugs, alcohol
* Testicular factors
o Genetic defects on the Y chromosome
+ Y chromosome microdeletions
o Abnormal set of chromosomes
+ Klinefelter syndrome
o Neoplasm, e.g. seminoma
o Idiopathic failure
o Cryptorchidism
o Varicocele
o Trauma
o Hydrocele
o Mumps
o Testicular dysgenesis syndrome
* Posttesticular causes
o Vas deferens obstruction
o Infection, e.g. prostatitis
o Retrograde ejaculation
o Hypospadias
o Impotence
o Acrosomal defect/egg penetration defect
* Smoking
o According to a study conducted by the American Society for Reproductive Medicine, smoking is one the most prominent factors contributing to low sperm count in men.
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.
In the majority of cases of male infertility and low sperm quality, no clear cause can be identified with current diagnostic methods. It has been speculated that random mutations of the Y chromosome may be an important factor. As the human Y chromosome is passed directly from father to son, it is not protected against accumulating copying errors, whereas other chromosomes are error corrected by recombining genetic information from mother and father. This may leave natural selection as the primary repair mechanism for the Y chromosome. Microdeletions in the Y chromosome have been found at a much higher rate in infertile men than in fertile controls and the correlation found may still go up as improved genetic testing techniques for the Y chromosome are developed. (Existing test kits for Y chromosome microdeletions with PCR markers cover only a tiny fraction of the chromosome's 23 million base pairs and therefore very likely still miss most mutations. The gold standard test for genetic mutation, namely complete DNA sequencing of a patient's Y chromosome, is still far too expensive for use in epidemiologic research or even clinical diagnostics.)
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.
|
Important notice:
The content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other
qualified health provider with any questions you may have regarding a medical condition.
|