As a woman of a certain age (35) who is hoping to have children, I’m flooded with information, suggestions and unsolicited advice about what motherhood (in the biological sense) might look like for me. “You really need to start soon!” is the phrase I hear ad nauseum from presumably well-meaning family and friends.

My fiancé, Patrick is pushing 40 and just as eager to raise kids as me, but the subject doesn’t much come up for him. He may be asked if he wants to be a dad, but never does his “yes” lead to a bombardment of follow-up questions and a recitation of scientific tidbits. I’m not arguing that he should be put through this awkward line of interrogation (frankly, I think we should both be left alone unless we’re asking for input), but surely, it says a lot about our society that nobody ever reminds him that to an extent, the biological clock is ticking for him, too. Perhaps they just don’t know that the risks for aging men surrounding fertility and the health off their offspring; after all, until I started to do the research, I had only a vague idea of them.

Things can start to change after 40

As a woman, I can say that I’ve heard the phrase “your eggs become geriatric when you’re 35” maybe 50 times since I turned 30. Turns out, men have their own ages to be mindful of.

“It's on a hockey stick shaped curve [of risks], just as it is with women, but with men the stick is a lot longer. The risks can start at 40 or maybe even 50 or 60 and then [risks] rapidly rise after 60,” says Dr. Paul Turek, a men’s health and fertility urologist.

Dr. Brian A. Levine, the founding partner and practice director of CCRM New York, board-certified in both reproductive endocrinology and infertility and obstetrics and gynecology targets 50 as the age where concerns about paternal aging may present themselves for men.

In terms of the age-old question, how old is too old? We don't know the answer to that.

“Despite men making sperm from puberty to death at the same rate, some of the sperm parameters start to change as men turn 50,” he says. “In terms of the age-old question, how old is too old? We don't know the answer to that. There are multiple factors, and it takes a lot to make a healthy child and the outcome is dependent on age of the mother, the father and the uterine environment. ”

Sperm is made throughout a man’s life, but the system can get rusty

Sperm is made new every three months, but when the system is aging there can be errors, explains Dr. Turek. “A thousand sperm per heartbeat [is produced], but in an older man it can be delivered with breaks. It’s like packing a vase and the factory is overheated and it doesn't get packaged well. That's what happens to DNA, and it can cause miscarriages and infertility.”

The problem here is that even with broken DNA, so to speak, a semen analysis (that you may get to test your fertility) can “look very normal,” says Dr. Turek. “With older women we know that most of the [problems] that can affect the offspring are chromosomal, leading to either miscarriages or terminations and, rarely, birth defects. But generally, this can all be detected, defined and diagnosed so we can make decisions about them. With men, you can't screen for these errors in the DNA that cause mutations unless you know of them ahead of time, but they tend to be new.”

Uncommon diseases and neurological issues

These errors tend to “easily get through quality control system [of the uterine environment] without causing miscarriage and can cause debilitating diseases in offspring like hemophilia, dwarfism and progeria,” says Dr. Turek. “Some of these are not picked up natally but [present] as children get older or become adults. Sometimes with older men you’ll see a successful childbirth and even a healthy child and then the issues hit.”

In the latter case, we tend to see epigenetic changes among certain gene sets that shape neurologic function. “These are neither mutations nor chromosome issues, just marks on DNA,” clarifies Dr. Turek. “Women do throw off mutations, but men do it five to ten times higher. And they tend to be neurodevelopmental features.”

Dr. Turek pinpoints the following risks for men over 40 (with the risks sharpening as the decades pass):

2-fold increased risk of miscarriage

2-fold increased risk of pre-term birth

1.9-fold increased risk of pre-term death

25 percent increased risk of birth defects

2-fold increased risk of chromosomal abnormalities

10-fold increased risk of disease due to single gene mutations

5-fold increased risk of childhood and adult diseases (such as autism schizophrenia, bipolar and epilepsy)

Older dads may live longer, as do their offspring

If you’re looking for the scientifically backed pros here, consider this: both older dads and their offspring tend to have longevity on their side.

“The good thing about being an older dad is that you tend to live longer, and you certainly have lots of young reasons to,” says Dr. Turek. “Your offspring also tends to live longer. We’re evolving a lot more rapidly and this system is trying to help us live longer, which is a plus for both the older dad and his child. So, it makes teleological sense that if you are healthy enough to reproduce at an older age, you’re good.”