In the 1950s, a baby born with a serious condition or with a low birth weight may have been less likely to survive than the child would be today. But the long term effect of this change may vary.
A recent study found that lifesaving technologies for babies may be a double-edged sword.
On the one hand, the rate of infant death among babies born under 5.5 pounds has decreased significantly since 1960.
This increase in survival is due to improved care in neonatal intensive care units. Yet, with more children surviving, there are also more living with an intellectual disability.
Another effect of improved NICU care, though, is that other children who survived without intellectual disability may have suffered brain damage if they had survived without NICU care.
The study, led by Jeffrey P. Brosco, MD, PhD, of the University of Miami and the Department of Pediatrics at Miller School of Medicine, aimed to find out whether children's intellectual development appeared affected by medical procedures in childhood.
The researchers looked at all the data in medical literature published from 1950 through 2000 on children in the US and in Western Europe. They looked for all conditions which appeared related to intellectual disability in children.
They also looked for evidence of how common these conditions were and whether they were related to the increased use of any medical interventions.
All the children included in the studies they reviewed had received some kind of medical treatment in the first five years of life that saved the child's life.
The children had also all been evaluated for intellectual ability after they were 5 years old.
Overall, the researchers found that 10 to 15 percent of all intellectual disabilities children had were related to being born with a low birth weight. Low birth weight is usually considered under about 5.5 pounds.
Therefore, the improved ability for medicine to save the lives of babies born with a low birth weight appears to have occurred alongside an increase in later intellectual disability. Without that medical intervention, however, the babies would likely have died.
The researchers did not find any other medical interventions over the past fifty years that were linked to an increase in intellectual disability.
One reason the researchers studied this topic was that past research had found newborn screening for two types of birth defects had decreased the percentage of people living with intellectual disability. Those birth defects were a thyroid deficiency and a metabolic disorder called phenylketonuria.
However, this study did not find evidence for a decrease in intellectual disability traced to earlier treatment of those birth conditions.
"These results suggest that other medical interventions, particularly the advent of intensive care technologies, have also increased the prevalence of intellectual disability," the researchers wrote.
The good news from this study, however, is that the children with these intellectual disabilities are likely to have been children who may not have survived in earlier eras without the intensive care treatment.
Also, children who might have survived with brain damage in an earlier era may now have less intellectual ability due to care in the NICU.
"It is possible that very recent advances in NICU care, such as improved ventilation technique and attention to the neonate’s developmental environment, may have lowered the contribution of low birth weight infants to the overall prevalence of intellectual disability," the authors wrote.
The study was published April 29 in the journal JAMA Pediatrics. The research was funded by a Robert Wood Johnson Foundation Generalist Scholar Award and an Arsht Distinguished Ethics Faculty Award at the University of Miami. The authors declared no conflicts of interest.