VANCOUVER, B.C. – Late preterm infants have a higher incidence of future neurodevelopmental problems than children born at term, two studies showed.
"Everyone has just assumed that late preterm babies are fine, and there are no long-term problems. We are now finding that the outcomes are probably not as good, and [we] need to find out whether just being born [early] is the problem, or whether it’s being born [early] and having something else going on," said investigator Dr. Elaine Boyle of the University of Leicester (England).
In the first project, a team from the University of Iowa in Iowa City performed structural brain MRIs on 52 children an average of 9.4 years old who were born at 34-36 weeks, and 74 children with a mean age of 10 years born at term. All were singletons.
Dr. Elaine Boyle
Among other findings, the mean volume of subcortical tissue was almost a quarter standard deviation lower in late preterm (LPT) children than in children born at term, a difference driven mostly by smaller thalami and hippocampi. "The structural difference on MRI directly related to areas in which the LPT cohort performed more poorly" on a battery of assessments, especially visual short-term memory (Pearson coefficient [r] = 0.3; P = .001) and processing speed (r = 0.2; P = .03), said lead investigator Dr. Jane Brumbaugh of the department of pediatrics at the University of Iowa.
At assessment, LPT children were 36 kg and 138 cm tall on average, with a head circumference of 54 cm. Children born at term were a bit bigger, an average of about 38 kg and 142 cm tall, with a head circumference of 55 cm. The analysis controlled for age, sex, and intracranial volume; there were no statistically significant between-group socioeconomic differences.
Meanwhile, Dr. Boyle’s team found that 16% (101/638) of infants born at 32-36 weeks, but just 10% (77/765) of term infants, had neurodevelopmental disabilities at age 2, according to the children’s parents (RR, 1.4; 95% CI, 1.1-2.0; P = .011).
The finding comes from the PARCA-R (Parent Report of Children’s Abilities–Revised), which the Leicester team administered to parents of 2-year-olds; the investigators did not confirm their findings with clinical assessments. Their results were adjusted for sex, socioeconomic status, and multiple births.
Parents also reported that 1.6% (10) of LPT but 0.3% (2) of term infants have some type of sensory impairment, and that LPT children show a trend toward more communication problems.
Male sex, lower socioeconomic status, prepregnancy hypertension, preeclampsia, and recreational drug use during pregnancy each more than doubled the risk of neurodevelopmental disability in LPT children.
"Late to moderately preterm infants have a 50% increased risk for neurodevelopmental disability at 2 years of age. As we see in the very preterm population, this is largely driven by cognitive problems," said lead investigator Samantha Johnson, Ph.D., of the University of Leicester.
Besides arguing for term birth when possible, intervening in preeclampsia, recreational drug use, and other problems might improve outcomes. Also, it might be a good idea to screen parents of LPT infants to identify children who could benefit from early intervention, she said.
The investigators said they have no relevant financial disclosures. The University of Iowa funded the MRI study, and the U.K. National Institute for Health Research funded the English study.