Preemie Risks Last into Adulthood

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Premature baby in an incubator.

Technology can be a very good thing, and in the medical world respirators and incubators can be lifesavers, especially for premature babies. But new research shows that even when preemies survive the precarious days of their early lives, they may have health issues that continue long after they come home from intensive care.

Reporting in the Journal of the American Medical Association this week, scientists at Duke University analyzed birth-registry records of over one million Norwegians born between 1967 and 1988 (about 5% of whom were born premature); unlike birth records in the U.S, those in Norway are cross-linked to sibling and parental records across generations, offering a richer set of data. Duke's Dr. Geeta Swamy and colleagues tracked people for up to 35 years to record their death rates. They also looked at how long babies had been in the womb at the time of their birth, a factor that the authors felt was a better indicator of a baby's development and maturity than, say, birth weight — a measurement many previous studies have used.

Doctors have long documented the immediate dangers of preterm birth — weakened immunity, respiratory problems and increased risk of death — but now, as neonatal technologies have allowed more and more preemies to survive past their early years into adulthood, the long-term data is beginning to emerge. Recent findings suggest that being born too early may have lasting consequences. Studies have linked preterm birth, defined as being born before 37 weeks gestation, with cognitive differences during children's elementary and high school years, for example, when preemies tend to exhibit developmental abnormalities and learning difficulties that full-term children do not. Now the new JAMA report suggests that premature babies' elevated risk of death also follows them well into adolescence — very preterm babies, born at 22 to 27 weeks, were twice as likely to die between the ages of six and 12 than their full-term counterparts.

More surprising were the longer-term consequences that Swamy's study documented for the first time: preemies who made it to adulthood, the data showed, were less likely to have children than other people and, when they did, were more likely to have premature infants themselves. After several decades, only 25% of the preterm women had had children, compared to 68% of women whose mothers had carried them to term, while 14% of the preterm men had reproduced, compared to half of the full-term men. "I think being born preterm has some effect on your development, your biological functioning," says Swamy. "Whether it affects your fertility is something that is up for research. But for men and women who are infertile, we might start asking about their birth history; we currently don't ask their birth weight, or how far along they were when they were born. It would be an interesting avenue for infertility research."

"This study provides interesting insights because it looks beyond childhood and into the adulthood of preterm individuals, as well as even into the next generation. It's an area that we have not really look at yet," says Dr. Wanda Barfield, a neonatologist at the Centers for Disease Control.

Like previous studies on preemies, Swamy's research found that men and women who were born preterm achieved less education than their full-term peers — not a surprise, since many preterm births occur among parents of lower socioeconomic status, who are less educated, more often unmarried and have higher rates of alcohol and tobacco use. Children born into these environments, studies have suggested, are more likely to adopt the behaviors and habits they see around them and thus may decide not to pursue higher education.

Swamy's report is particularly significant given that more babies are now being born preterm — intentionally. Good prenatal care means healthier mothers and babies, but it also means that doctors are earlier to catch conditions that might jeopardize either the baby or the mother. Preliminary signs of diabetes in the mother or preeclampsia, a condition in which the mother becomes hypertensive, may lead a doctor to deliver a baby preterm. Granted, these babies are closer to reaching term, but they are still born before the ideal 37-to-41-week period and, according to Swamy's findings, still at increased risk compared with full-term babies. So, if Swamy's results are replicated, doctors may have to reconsider their practice, and focus their attention on preventing these conditions from developing in the first place.

Swamy certainly hopes that will be the case. Her findings, coupled with the growing body of evidence on the short-term health issues of preemies, argues that being born too early leads to certain basic biological consequences that even high-tech neonatal medicine cannot erase. "This study demonstrates that the issue of prematurity is a public health issue," says Barfield. "So our focus should be on the prevention of preterm delivery in the first place. Our goal should be to give women the opportunity to have healthy pregnancies where babies go to term." And that would be one less thing for anxious mothers to worry about.