"More than a dozen years after fertility specialists learned to turn all-but-sterile men into fathers, scientists are awaiting answers to a looming question: What about the sons?

One of the central concerns centers on the possibility of chromosomal abnormalities leading to male infertility. As puberty kicks in, scientists believe they may start to see sons who’ve inherited the problems of their fathers, an issue that many couples may not have considered in their quest to have children.
“This is the generation we’ve created,” said Dr. Tommaso Falcone, who chairs the obstetrics and gynecology department at the Cleveland Clinic and directs the Reproductive Endocrinology Research Laboratory. “We may have tens of thousands of boys born with infertility.”

Genetic fallout for ICSI sons is still a largely unexplored issue in the field of infertility, which affects an estimated one in eight couples in the United States, or about 7.3 million people, according to RESOLVE, a national infertility group. Up to 40 percent of cases are attributed to problems with the man, including damaged sperm, low sperm or no sperm at all.

Of the more than 52,000 babies born using IVF in the U.S. each year, between 8,000 and 9,000 are the offspring of male factor fathers, according to Falcone.

“We tell parents there could be a genetic cost to this,” he said.

Basic facts about infertility are fueling scientists' concerns. In women, infertility is most often caused by a physical problem such as blocked fallopian tubes or scar tissue caused by endometriosis, issues that aren't likely to be inherited by their daughters. When IVF was pioneered three decades ago, it solved many of those problems by providing a way to get the sperm and egg together outside the woman.

In men, however, it's not so clear cut. Doctors don't know what causes infertility in about half the cases, but think that many men's infertility problems may be rooted in their genes.

Last year, Danish researchers reported that levels of the male sex hormone testosterone were lower in baby boys produced through ICSI than in those conceived naturally. "