Newborn babies’ brains grow one percent a day
A baby’s brain is a mystery whose secrets scientists are beginning to unravel. The first study of its kind shows that newborn babies’ brains are about a third the size of an adult’s at birth, and grow at an average rate of 1% a day to reach just over half the size of an adult’s brain within three months.
The study, carried out by researchers from the University of California, the University of Hawaii and the Norwegian University of Science and Technology, aimed to map newborns’ brains during their first three months of life. This cognitive research was published on August 11th, 2014 in the peer-reviewed medical journal, JAMA Neurology.
For centuries doctors have estimated brain growth using measuring tape to chart a baby’s head circumference over time. Any changes to normal growth patterns are monitored closely as they can suggest problems with development. But as head shapes vary, these tape measurements are not always accurate.
Thus for this study, researchers used a new scanning technique to measure the early development of newborn brains. They set out to map growth trajectories in the brains of newborn babies during the first three months of their life. Using a series of magnetic resonance imaging (MRI) scans, the volume of multiple brain regions and the growth rate of the newborn brain could be calculated. MRI works by executing high-quality images of a range of brain regions, without the use of radiation. One huge advantage of earlier charting of the size and rate of brain growth is that it could help to detect potential signs of developmental disorders in the brain, such as autism. If a developmental disorder is seen to be present, treatment will be more effective than if detected at a later stage.
Researchers scanned the brains of 87 healthy newborns 211 times, starting when the babies were only 2 days old. They found that the newborn brain grows extraordinarily fast right after birth, but slows down to a growth rate of 0.4 percent per day by the end of three months.
Overall, infants’ brains grew by 64 percent in the first 90 days, according to the study. The average brain size was 20 cubic inches (341 cubic centimeters) at birth, and 34 cubic inches (558 cubic cm) at 90 days. In other words, the brains of newborns grew from about 33 percent of the average adult brain size to 55 percent of it in three months.
The researchers noted that the brains of the infants who were born one week earlier than the average in the study (about 38 weeks), were 5 percent smaller than the average. By the end of the three months, the difference between these babies, which the researchers said were preterm, and the full-term babies became smaller, but the preterm babies hadn’t fully caught up, and their brain size was 2 percent smaller than the average, according to the study,
“The brains of premature babies actually grow faster than those of term-born babies, but that’s because they’re effectively younger — and younger means faster growth,” study researcher Dominic Holland, of the University of California, San Diego School of Medicine, said in a statement. The findings suggest that inducing labor early, without a medical reason, may have a negative effect on the baby’s cognitive development, Holland said.
Researchers say using MRI scans will prove to be a much more effective way to track cognitive development. Scans should lead to more exact growth charts, replacing the old method of measuring the skull with measuring tape, and help identify disorders such as autism or brain injury early.
Scientists will now investigate whether alcohol and drug consumption during pregnancy alters brain size at birth.