Boys conceived through a common type of in vitro fertilization procedure may produce less sperm and experience more struggles with fertility than peers born the old fashioned way, a recent study suggests.

Researchers focused on 54 men conceived by what's known as intracytoplasmic sperm injection (ICSI), a technique developed in the 1990s to treat cases when infertility is tied to problems with a man's sperm.

Compared to a control group of similar men conceived naturally, the ICSI group had much lower average sperm concentration, total sperm count and total motile or active sperm count.

"This study indicates that ICSI done for severe male factor infertility may lead to the same condition as the one in the father," said study co-author Andre Van Steirteghem of the Center for Reproductive Medicine at the University Hospital of Vriije University in Brussels.

"One should inform the couples about this," Van Steirteghem added by email.

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Before ICSI became available, couples that had infertility due to male sperm issues could only conceive using IVF techniques involving a sperm donor, Van Steirteghem said.

With ICSI, clinicians harvest sperm from the father. In a lab, they inject only the healthiest sperm into an egg from the mother, and then they implant the fertilized egg in the mother's womb.

For men who have very few viable sperm, this means that the fertility experts can choose the best quality sperm and ensure it fertilizes the egg by injecting the sperm rather than leaving it to swim to the egg unaided.

The men conceived by ICSI in the study were between age 18 and 22, among the first people born using this technique.

They had almost half the sperm concentration and a two-fold lower total sperm count and total count of motile sperm that could swim well than the men their age that were conceived naturally, researchers report in the journal Human Reproduction.

In addition, compared to men born after spontaneous conception, ICSI men were nearly three times more likely to have sperm concentrations below 15 million per milliliter of semen, which is the World Health Organization's definition of "normal," and four times more likely to have total sperm counts below 39 million.

The researchers adjusted their results for factors that could affect semen quality, such as age, body weight, genital malformations, time from ejaculation to analysis and abstinence period.

Although sperm concentrations and counts were lower in the ICSI men than in their spontaneously conceived peers, the researchers also found that a low sperm concentration and total motile sperm count in fathers did not necessarily match the values found in their sons.

Because male infertility issues can be inherited by male offspring, the study results aren't entirely surprising, the authors note. It's still possible, though, that some couples might want to consider alternative IVF options such as donor sperm to avoid passing on this problem, researchers note.

"Whilst the data from the present paper shows that the sperm quality of ICSI born adult males is noticeably lower than that seen in men who were conceived naturally it also shows that there appears to be a poor relationship between the sperm quality of ICSI-born males and their fathers," said Allan Pacey, a researcher at the University of Sheffield in the U.K. who wasn't involved in the study.

"This means that it doesn't automatically follow that ICSI-conceived males will always have the poor fertility seen by their fathers," Pacey added by email.

Rather, the results suggest that some men conceived by ICSI may still be able to father children naturally, said Richard Sharpe, a reproductive health researcher at the University of Edinburgh who wasn't involved in the study.

It does make sense for them to start trying to conceive when they - and their partners - are younger because fertility odds decline with age, Sharpe said by email.

But they need not assume a natural conception is out of the question.

"There is no reason for them to seek infertility help or advice until they have tried to father children by intercourse for a couple of years," Sharpe said.