I've been writing for awhile about "assaults" on fertility. Here's yet another angle I didn't know much about until recently.
Apparently, people born prematurely are at higher risk for not becoming parents as adults. With more than 500,000 babies born prematurely in America each year, that's got to be a concern for many people.
The basis for this unsettling news is two studies published last year, based on data from Norway.
Norway, like the rest of Europe, has depressed fertility rates, so I thought maybe cultural influences were at play instead of premature birth. I interviewed a fertility specialist, Dr. Jeffrey Youngkin, who has run the Austin Fertility Center in Texas for more than two decades, and he said the studies are credible.
Norway tracks its citizens quite closely, he said, so it's possible to study long-term outcomes for people based on their gestational age at birth.
When researchers examined life events of Norwegians born from the 1960s to the 2000s, Dr. Youngkin said, "they found that both men and women who are born prematurely were less likely to have children."
"Of course, the vast number of premature infants did fine," he said, "but still, there were a good number that weren't able to conceive."
Both studies showed gestational age mattered.
"The earlier you were born prematurely, the more dramatic the effect was — the less likely you were to have a baby," Dr. Youngkin said. "It wasn't until 34-36 weeks [gestation] that their reproduction was pretty much equal" to people born at full term, those born at 37 weeks and after.
For instance, among Norwegians born at 23 to 27 weeks gestation, only 13 percent of men and 25 percent of women had become parents by their early 30s, said the study published in July in the Journal of the American Medical Association by researchers at Duke University Medical Center and University of Bergen in Norway.
The second study, also out of the University of Bergen and published in July in the New England Journal of Medicine, took the data a step further and excluded "preemies" who were receiving disability payments as adults. But it, too, found that persons born very prematurely were less likely to have children — 29 percent of these preemies were parents by ages 20 to 36, compared with 43 percent of persons born at full term.
"So that showed that even if you don't have any problem that's severe enough to get disability in Norway," being born prematurely is a risk factor for not having a child, Dr. Youngkin said.
The Norway studies didn't examine why preemies are less likely to become parents, but other research has found they are less likely to live on their own, live with a romantic partner or be sexually active.
In America, the rate of preterm births has hovered between 12 percent and 13 percent since 2000. New 2007 birth data from the National Center for Health Statistics shows a 1 percent decrease in the preterm rate, but at 12.7 percent, that's still 548,000 babies.
Preterm children already have well-known risks for disabilities, including cerebral palsy, lung problems, mental retardation, learning and behavioral problems, and vision and hearing loss. Studies also suggest a connection to autism.
Adding impaired fertility or infertility to this list seems so cruel, especially when these "miracle" children already have fought and won a battle to live.
But forewarned is forearmed, and Dr. Youngkin's advice to women who want to avoid preterm birth is pretty straightforward.
"Don't smoke," he says. "Protect yourself from sexually transmitted diseases. Get good medical care and have babies early in life. Don't put it off."
• Cheryl Wetzstein can be reached at firstname.lastname@example.org.