Professor Sukchareon and his team had been studying men with obstructive azoospermia, a condition where sperm are created but cannot be mixed with the ejaculatory fluid due to a physical obstruction (such as a vasectomy). He found that they had high rates of chromosomal aneuploidy (where an abnormal number of specific chromosomes or chromosome sets exist within the nucleus of the cell) and diploidy (containing two sets of chromosomes ?unlike most cells in the body, the sex cells should only contain one set of chromosomes.
"The rate of abnormality was about 10 times higher than the aneuploidy and diploidy rate in normal fertile men", said Professor Sukchareon. "This raised a lot of questions, so we decided to study the rates of these abnormalities in ejaculated sperm after vasectomy reversal. If these sperm continued to have a high rate of aneuploidy and diploidy, we would know that obstruction by vasectomy must affect spermatogenesis in the longer term."
The scientists found a significant correlation between the duration of the obstruction in post vasectomy-reversal men and the number of abnormal sperm, and also between the time interval after vasectomy reversal and the total sex chromosome aneuploidy rate ?i.e. the long ago the reversal the better the chances of producing normal sperm.
"This study raises a lot of questions", said Professor Sukcharoen. "Is the abnormal spermato genesis reversible, and if so, how long will it take before things get back to normal? Perhaps more importantly, will babies born after vasectomy reversal ?either conceived naturally or by ART ?have problems themselves?"
To date there have been no studies looking at these questions, he said, and his team are beginning the follow-up research. "We are collecting sperm during vasectomy reversal operations and will compare the aneuploidy rate of these and of the sperm we will collect each month in the future from the same men. This will help us understand what the dangers are. But in the meantime, I think that doctors need to be very aware of the possibility that babies born after vasectomy reversal may have problems."
Their findings may not affect babies conceived naturally after such a procedure, says Professor Sukchareon, since the female genital tract may select the best sperm for fertilisation. "But this is still uncertain, and until we know more it would probably be safer to freeze ejaculated sperm before vasectomy. We need a lot more evidence and research on this issue before we can be certain of avoiding the dangers."