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Bucking the notion that being born a few weeks early has no discernible impact on babies, a new study indicates that "late pre-term" infants face more developmental delays than their full-term peers and those delays may affect their school performance.
Researchers in Boston analysed records from 6,300 term and 1,200 late pre-term infants - those born between 34 weeks and 37 weeks gestation - from the Early Childhood Longitudinal Study-Birth Cohort, using equations to estimate the odds of mental or physical delays among the pre-term set at the age of two.
In mental skills, late pre-term babies were 52% more likely than term infants to suffer severe delays and 43% more likely to experience milder limitations. In motor skills, the pre-term toddlers faced 56% increased odds of severe delays and a 58% increased risk of milder ones.
The study is reported in the journal Pediatrics.
Elective births more common
"Previously, these infants were just considered small full-term infants rather than pre-term infants," said study author Dr Melissa A. Woythaler, a neonatologist at Massachusetts General Hospital. "There's been a shift in how they're viewed."
Pre-term births - those in which babies are delivered before 37 weeks' gestation - account for nearly 13% of the nation's 4.2 million annual births, according to the study. Late pre-term births have risen 25% since 1990, from about 7 to 9% of all births.
In addition, 5 % to 40% of US births are now early elective deliveries, meaning that births are induced pre-term without a valid medical reason, according to a recent hospital-by-hospital report from the Leapfrog Group, a national employer-driven hospital watchdog group.
Noting that many of these at-risk infants receive little or no specialised developmental follow-up, Woythaler's data included babies with at least 34 weeks' gestation from wide economic and racial backgrounds who received complete assessments near the age of two.
The brain of a baby at 34 weeks' gestation weighs 35% less than it would at term, the study noted.
Social factors and gender had the greatest impact on the children's mental scores, the study said, with language spoken at home playing a key role. (Boys were most likely to have severe development delays.) In contrast, gestational age was the most important contributor to physical delays.
Babies should ideally be delivered full-term
Researchers noted a few study limitations, including the lack of information on possible newborn medical complications and the possible weaknesses of infant developmental testing.
However, their findings are consistent with those of other recent studies of late pre-term infants, they said. Researchers have found such infants are at higher risk for respiratory problems, worse academic performance and school suspension down the road.
"There's a reason why normal gestation is 40 weeks," said Dr Marty Ellington Jr., chairman of the department of paediatrics at Lenox Hill Hospital in New York City. "If a child needs to be delivered for a maternal or infant medical condition, care has advanced where those children can do quite well. But we should never discount the importance of those two to four weeks. If we have a choice, we would want the child to go to term."
Woythaler said more research is needed to determine how to best help pre-term babies suffering developmental delays reach the same level as their peers carried to term.
"Very premature infants automatically get referred to early intervention," she said. "Not these infants. Not all of these infants are doing poorly - a lot are doing well and normally. Once we can pinpoint which infants can benefit from early intervention, that's the point we can do something."
Early births, learning difficulties
Ellington pointed out that gender and medical issues that contribute to developmental delays in this group can't be changed, but "the social component is modifiable with respect to early intervention programmes".
"When put into a whole, [the delays] can significantly impact a child's performance, particularly as they reach school age," he said. "They compound each other and make it difficult for a child to function in a normal classroom."
But the high cost of valuable early intervention programmes - typically including occupational, physical and/or speech therapy - has caused many across the country to be eliminated, Ellington said.
"It's something very concerning, given the vast numbers of infants that are having these developmental problems," he said.
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