Column 5 min read

Genome Culture: Young Women Are Freezing Their Eggs. Should Men Freeze Their Sperm?

Men get old too.

By Laura Hercher featured image PhonlamaiPhoto / Getty Images

I don’t know who coined the phrase “women get old and men get distinguished,” but it isn’t true. Mother Nature sayeth otherwise. Young women who delay childbearing are regularly lectured on the risks associated with aging eggs: a higher incidence of chromosome disorders like Down syndrome, more miscarriages, infertility, and so on. Now that egg freezing is possible, it is aggressively marketed to women in their thirties and even younger via campaigns designed to remind them of their risk. But the biological clock does not tick-tock for women alone.

Men have similar risks, but they are less likely to hear about it. Men’s sperm decline in quality and quantity as they age. As with women, this trend begins after age 35 and accelerates after 40. But there is no hard limit on the age at which men can, in theory, father a child. This, however, can be misleading. Well-publicized examples of late-in-life offspring may contribute to a confidence in male fertility that obscures biological realities.

As the prospective father ages, couples are less likely to conceive, even when his partner is in her twenties. That’s because fertilization is a process that has evolved to test sperm quality, and the egg is a fortress designed for that purpose. Older men produce fewer, slower sperm that are less often able to storm the castle or breach its walls.

When couples do achieve a pregnancy, there are questions about how advancing age might affect the health of the child, and again, there are risks related with increasing age in both the mother and the father. But the risks associated with advanced paternal age are much less publicized.

An older father is more likely to pass along some harmful genetic changes.  A variety of rare conditions are a bit less rare among children of older fathers. These include certain skeletal dysplasias, some cancer-causing syndromes, and the most common form of dwarfism. Advancing paternal age has also been shown to increase a child’s risk for both schizophrenia and autism.

The risks of having an older mother or an older father are analogous but not identical, because until the moment of their union, eggs and sperm live very different lives. Females produce a vast quantity of eggs early in development and warehouse them until they are needed. In fact, it is ironic that it took us so long to figure out how to freeze eggs because, biologically speaking, they are quite at home in a state of suspended animation. That’s how they hang, most of the time. A handful of eggs mature each month after puberty, and usually only a single egg becomes available for fertilization. When fertilization occurs, that egg splits its chromosome pairs in two, making room for dad to contribute half the embryo’s DNA. But older eggs perform this splitting business less reliably, so the resultant embryos are at greater risk of ending up with all or part of a chromosome deleted or repeated.

Sperm, on the other hand, don’t get stockpiled, and must be continually regenerated throughout a man’s fertile life span. This means that the sperm precursors start duplicating and dividing at puberty, and just keep going. Over time, they accumulate errors — not big changes, but small changes — like the substitution of one base pair for another in the DNA.

Although the changes are small, their consequences can be serious. What differentiates these changes from those associated with older eggs is not that one is more significant than the other; it is that one is amenable to testing and the other is not. Prenatal testing is good at identifying the type of chromosome anomalies that are more common as women age. We’ve been doing those tests for decades and, for this reason and others, we tend to discuss women’s options and risks of childbearing at an older age. But we don’t have a test to offer for the things associated with advanced paternal age, nor is one on the horizon. So when it comes to older dads, it’s crickets from the medical community.

But even without a test, men have options if they understand their risks: They can have their children earlier, or they can freeze their sperm. We freeze sperm for IVF and sperm donation all the time. We know that it’s not dangerous; it’s not expensive; it’s not invasive; and it works. It’s actually an easier procedure and a safer bet for achieving pregnancy than egg freezing. So why is there an entire cottage industry hawking egg freezing and nary a mention of sperm?

We don’t market to men because they don’t know that advanced paternal age is an issue. Our failure to discuss the risks associated with advanced paternal age isn’t just a medical phenomenon, it’s a social phenomenon. We’ve bought into a narrative that suggests fertility is a woman’s concern and infertility is a woman’s fault. No one talks to men about the dangers of postponing fatherhood because people think it’s a women’s issue, and the fact that we don’t talk about it perpetuates this false and dispiriting notion.

Making women feel the world is a bit less unfair is a noble goal, but there are even better reasons why it’s important to discuss the negative effects of advanced paternal age. I know it’s hard to ask men to give up the myth of ageless male fecundity, but it’s empowering as well. Men, their partners, and the next generation deserve a real conversation about parenthood and the consequences of aging.

  • Grey Genetics

    Great piece on a topic that should get more discussion than it does. “As with women, this trend begins after age 35 and accelerates after 40.” – it’s also a not uncommon misconception that the decline in quality and quantity of eggs begins at 35. It really begins long before but just accelerates with age, with 35 singled out as a tipping point at least to some extent for historical reasons. I know the author knows this, but it may be an important point of clarification for readers.