Aging not only affects a man’s fertility, the study found, but becoming a father late in life also increases the risk that the mother of the child — no matter what her age — will have complications during pregnancy and that the child will have health problems.
“While it is widely accepted that physiological changes that occur in women after 35 can affect conception, pregnancy and the health of the child, most men do not realize their advanced age can have a similar impact,” says Dr. Gloria Bachmann, one of the authors of the study and a professor of obstetrics and gynecology at Rutgers University, in a released statement.
As Bachmann and her colleagues point out in their paper, the medical community has not agreed on what is an advanced age for fatherhood. Some say it begins at 35, while others suggest 45. What is clear is that an increasing number of men in the United States are becoming fathers during middle age or beyond. The number of infants born to fathers older than 45 has risen by 10 percent during the past four decades.
That increase is being driven by several factors, say the researchers, including the widespread use of contraceptives, more effective reproductive-assisted technologies, a greater number of later and second marriages, and a longer life expectancy.
A literature review
For the study, Bachmann and her colleagues reviewed 40 years of research on paternal age and its effects on fertility, pregnancy complications and the health of children.
They found that as men age, their fertility declines. Some research has suggested, for example, that men aged 45 or older who want to become fathers are four to five times more likely than men aged 24 or younger to take more than a year to conceive a child with their partners — even if their partner is younger than 25. By comparison, women older than 35 are only twice as likely as women younger than 25 to take more than a year to conceive.
Studies have also found that the sperm of older men can be damaged in ways that affect its fertilization potential during artificial insemination or in vitro fertilization. For this reason, some sperm banks limit their donors to men younger than 35.
Older fathers can also put their partners at increased risk for pregnancy and birthing complications, including gestational diabetes, preeclampsia and preterm birth. One study found, for example, that the partners of men aged 46 or older were 28 percent more likely to develop gestational diabetes than the partners of men aged 25 to 34 years.
In addition, infants born to older fathers are at a higher risk for low birth weight, low APGAR scores (a quick way of assessing the physical health of newborns), newborn seizures, and birth defects, such as congenital heart disease and cleft palate. The study also found that the children of older fathers have an increased likelihood of developing childhood cancers, psychiatric disorders and autism.
“Although it is well documented that children of older fathers are more likely to be diagnosed with schizophrenia — one in 141 infants with fathers under 25 versus one in 47 with fathers over 50 — the reason is not well understood,” Bachmann says.
“Also, some studies have shown that the risk of autism starts to increase when the father is 30, plateaus after 40 and then increases again at 50,” she adds.
Most of these outcomes, Bachmann and her colleagues note in their paper, result from the fact that aging leads to a natural decline in testosterone, more damaged sperm and poorer-quality semen. But some of the associations can’t be explain and need more research.
“In addition to advancing paternal age being associated with an increased risk of male infertility, there appears to be other adverse changes that may occur to the sperm with aging,” says Bachmann. “For example, just as people lose muscle strength, flexibility and endurance with age, in men, sperm also tend to lose ‘fitness’ over the life cycle.”
Reproductive counseling should be considered for older men as well as for older women, she and her colleagues stress in the conclusion of their paper. They also suggest that sperm banking “may be an option for men who are planning to delay fatherhood.”
FMI: You’ll find an abstract of the study on the website for Maturitas, but the full paper is behind a paywall.