WEDNESDAY, June 21 (HealthDay News) -- Men who undergo vasectomy reversal may be at significantly higher risk of producing abnormal sperm and possibly even causing birth defects in children, a new study suggests.

Researchers at Chulalongkorn University, Bangkok, Thailand, studied men who had undergone a procedure -- such as a vasectomy -- that caused sperm to be produced but kept separate from their semen.

Studying their ejaculatory fluid, the researchers noted that these men had significantly higher rates of abnormal chromosomes than men who had not undergone such a procedure.

Specifically, these patients showed higher rates of a condition called chromosomal aneuploidy, in which atypical numbers of chromosomes or sets of chromosomes appear within a cell's nucleus. They also showed higher rates of diploidy, meaning that two sets -- rather than the one that normally appears -- of chromosomes appear in the nuclei of sex cells.

"The rate of abnormality was about 10 times higher than the aneuploidy and diploidy rate in normal fertile men," researcher Nares Sukchareon, from the university's Department of Obstetrics and Gynecology, said in a prepared statement. "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 researchers even noted a discrepancy in abnormalities in the sperm and the time lapsed since the vasectomy reversal was completed, and the amount of time the vasectomy was in place.

"This study raises a lot of questions. Is the abnormal spermatogenesis reversible, and if so, how long will it take before things get back to normal?" Sukchareon asked. He also questioned whether or not children born to such fathers would have abnormalities themselves.

Although Sukchereon concluded that the results from this study may not mean that babies born to men who have undergone vasectomy reversals will have birth defects, "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," Sukchareon added.

As a follow-up to this study, which was expected to be presented at this week's European Society of Human Reproduction and Embryology meeting in Prague, Czech Republic, the team is also already preparing the next step of the 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," Sukchareon continued. "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."

More information

Head to Planned Parenthood to find out more about vasectomies.