The risk of serious medical and social disabilities in adulthood increases sharply with decreasing gestational age at birth, according to a report in the New England Journal of Medicine.
Even young adults who were born preterm but have no lingering medical disabilities are at high risk of failing to complete high school, earning a low income, and failing to marry or have children, said Dr. Dag Moster of the University of Bergen (Norway) and his associates.
The researchers assessed the relationship between gestational age at birth and outcomes in adulthood because “the increased prevalence of medical disabilities, learning difficulties, and behavioral and psychological problems among surviving preterm infants has raised concerns that these infants may have difficulties in coping with adult life.”
They examined the issue using data from compulsory national registries of birth, education, job-related income, disability payments, and criminal records, tracking a cohort of 867,692 people born during 1967-1983 and followed until when they were aged 20-36 years.
The risk of serious medical disabilities such as cerebral palsy, blindness or severely impaired vision, hearing loss, and epilepsy increased markedly with decreasing gestational age, as did the risk of mental retardation and psychological, behavioral, and emotional disorders.
“At 19-35 years of age, nearly 1 of 9 persons who had been born at 23-27 weeks of gestation received a disability pension, as compared with 1 of 12 who had been born at 28-30 weeks, 1 of 24 born at 31-33 weeks, 1 of 42 born at 34-36 weeks, and 1 of 59 born at term,” Dr. Moster and his associates said (N. Engl. J. Med. 2008;359:262-73).
Even when people with residual medical disabilities were excluded from the analysis, a lower gestational age at birth was associated with a reduced likelihood of completing high school or higher education and of earning a high income. It also was linked to a low likelihood of finding a life partner and of having children.
“We also observed a significant association of autism spectrum disorders with very low gestational age,” but “caution is warranted interpreting this finding given the small number of cases in the very premature groups,” the researchers noted.
These results are consistent with those of other studies showing a link between preterm birth and “specific difficulties in the areas of motor, cognitive, behavioral, psychological, and social function among preschool and school-aged children,” Dr. Moster and his colleagues said.
The adverse outcomes in adulthood “may represent long-term effects of subtle brain dysfunction caused by preterm birth,” or they may be related to biologic and social factors underlying both the preterm birth and its later sequelae, they added.
Despite their study's findings on disability prevalence, the researchers wrote, “It should be recognized that a large proportion of the adults who were born prematurely and did not have severe medical disabilities completed higher education and seem to be functioning well.”