A team of researchers from the Lawrence Livermore Laboratory have presented evidence that chemotherapy treatment may adversely alter sperm on a temporary basis.

Abnormalities in sperm make it unwise for men to father children while undergoing chemotherapy treatment because of the increased risk of having a defective offspring. Missing or extra chromosomes commonly kill a fetus in the womb or cause birth defects.

This work was published in the May issue of the scientific journal Nature Genetics and includes the results of an eight-year study of men with Hodgkins disease, a cancer of white blood cells. This disease tends to strike people between the ages of 20 and 40 which is the parental age when most children are conceived.

The research focused on the sex chromosomes, known as X and Y, but also included chromosome 8 because it responds to fluorescent dye better than other chromosomes.

Among the patients studied during this research project, the number of sperm with extra or missing X, Y or number 8 chromosomes increased five-fold during chemotherapy treatment, according to the researchers.

It was also noted by the research team that the effect was temporary. About 100 days after treatment ended, the abnormal sperm counts had returned to pre-treatment levels.

Disorders in chromosomes are very common. In fact, about 7 in every 1,000 births will be affected by a chromosomal disorder. A chromosome abnormality is something that can be seen under a microscope.

In recent years the understanding of chromosomes and what can go wrong with them has greatly improved and expanded. The most frequently occuring chromosome abnormality and the leading genetic cause of mental retardation is Down Syndrome. Down Syndrome usually occurs when there is an extra chromosome 21.