Causes of Infertility
At least 10 percent of couples trying to have a child experience difficulties in achieving a pregnancy. Customarily, infertility is regarded as a failure to conceive during a year of regular, unprotected intercourse. This arbitrary 12-month period serves as an indication for medical consultation which, nevertheless, may ultimately show no specific fertility problem, with pregnancy occurring some time after a year.
Many causes of infertility affect both men and women. Such causes can be considered in two groups—those due to acquired conditions and those due to genetic disorders. Acquired causes include infection (for example bacterial and viral), numerous illnesses interfering with hormone production and control of egg and sperm production, radiotherapy (X-ray treatment, but not diagnostic X-rays), conditions that interfere with the blood supply to the testes or ovaries, and chemotherapy, just to name a few.
Genetic causes may be due to chromosomal abnormalities or to a defect (mutation) in a gene. For both acquired and genetic conditions, pregnancy may be achieved, but the embryo is lost at the time of the first expected missed period, which may occur without delay and appear normal or be characterized by a larger or smaller than expected menstrual flow. Exquisitely sensitive blood hormone tests can detect these "biochemical pregnancies" before they are lost.
Recognizing that pregnancies are being achieved yet lost so early helps focus attention on a specific set of causes that may differ from those underlying the problem in achieving an actual fertilization. Let's consider some of the more important genetic aspects of male infertility.