For years, IVF has been a beacon of hope for couples struggling to conceive.
But new research has uncovered an unsettling trend: boys conceived through a specific type of IVF procedure, designed to combat male infertility, are showing significantly lower sperm counts and quality as adults.
Could fathers unknowingly be passing their fertility struggles onto their sons?
A Window Into the Future
A team of Belgian researchers from Vrije Universiteit Brussel has conducted the most detailed study to date on male fertility among children conceived using intracytoplasmic sperm injection (ICSI)—a specialized IVF technique introduced in the 1990s.
Unlike traditional IVF, where sperm fertilizes an egg in a petri dish naturally, ICSI involves injecting a single sperm cell directly into an egg.
Initially developed for men with severe fertility issues, ICSI has since become the most widely used IVF technique in cases of male infertility.
Today, nearly half of all IVF treatments in the UK involve ICSI.
But until now, no one has thoroughly examined whether boys conceived through ICSI inherit their fathers’ fertility challenges.
To answer this question, the researchers studied 54 young men—now aged between 18 and 22—who were among the first people conceived using ICSI.
Their sperm quality was then compared with 57 men of the same age who were conceived naturally.
The results were striking.
ICSI Sons Have Three Times the Risk of Low Sperm Concentration
After accounting for factors like age, body mass index (BMI), and recent sexual activity, the findings revealed:
- ICSI-conceived men were three times more likely to have a sperm concentration below the normal threshold of 15 million sperm per milliliter.
- They were four times more likely to have a sperm count below 39 million—a number linked to lower chances of conception.
- The naturally conceived men had over double the amount of motile sperm, meaning their sperm had a better chance of swimming to and fertilizing an egg.
A Genetic Link—or Something More?
At this point, you might be wondering: does this prove male infertility is inherited? Not quite.
The study provides compelling evidence that fertility problems can be passed from father to son, but it doesn’t confirm a direct genetic cause.
In fact, when researchers compared sperm concentration and total motile sperm count between fathers and sons, the values did not correlate precisely—only the overall trend did.
That raises an intriguing possibility: could environmental or lifestyle factors also be at play?
Does ICSI Itself Play a Role in Lower Sperm Quality?
Here’s where things take an unexpected turn. While the study suggests a connection between fathers’ and sons’ fertility, it stops short of blaming ICSI itself for lower sperm counts.
In other words, the IVF procedure isn’t necessarily making things worse—it may simply be allowing men with fertility problems to have children who inherit the same issues.
As André Van Steirteghem, one of the pioneers of ICSI, explains:
“These first results from the oldest group of ICSI-conceived adults indicate that a degree of ‘sub-fertility’ has, indeed, been passed on to sons of fathers who underwent ICSI because of impaired semen characteristics.”
However, he cautions that correlation is not causation.
While genetic factors do play a role in male infertility, other influences—such as diet, lifestyle, and environmental exposures—may also contribute.
What This Means for the Future of Male Fertility
Perhaps the most surprising finding of all? Despite their lower sperm quality, the ICSI-conceived men hadn’t reported any fertility issues yet.
This means that even though their sperm counts were lower than average, they hadn’t necessarily struggled to conceive children of their own—at least, not yet.
But as these men grow older and begin trying to start families, researchers will be watching closely.
The big question remains: Will their lower sperm counts translate into real-world fertility problems?
The Next Steps in IVF Research
For now, scientists are calling for larger studies and genetic analyses to determine if male infertility is indeed passed down through generations.
The UK National Health Service (NHS) weighed in, stating:
“This finding supports concerns that the infertility of a father could be passed on to male offspring, but does not prove it.”
More research is needed, but this study highlights an issue that fertility specialists and hopeful parents should be aware of.
If male infertility can be inherited, then understanding its root causes could be crucial for improving fertility treatments in the future.
What Should Men Trying to Conceive Do?
If you or someone you know is considering IVF—especially ICSI—what should you take away from this study? While there’s no need to panic, it’s a good idea to:
Have a full fertility assessment before starting IVF.
Consider lifestyle changes that can boost sperm health, such as maintaining a healthy diet, avoiding smoking and excessive alcohol, and reducing stress.
Discuss the findings with your doctor to understand potential risks and alternative treatments.
With reproductive science advancing rapidly, one thing is clear: we are only just beginning to understand the long-term effects of assisted reproduction.
The children of the first ICSI generation are now adults, and their fertility journeys may shape the future of IVF for generations to come.
