How Does the Newborn Brain Adapt in the First Days of Life?

How does a newborn’s brain adapt so quickly to life outside the womb? New research from the New York University (NYU) School of Medicine provides the clearest picture yet of this transformation.

Published in PLOS Biology, the study maps the rapid reorganization of brain networks across the perinatal period, revealing distinct growth patterns that lay the foundation for sensory, motor and cognitive development.

Understanding brain development at birth

The transition from the womb to the outside world is one of the most dramatic transformations in human development. During this period, the brain must adapt quickly, coordinating a shift from the intrauterine environment to the complex demands of life outside. This requires reorganization across numerous systems, with neural connections undergoing remarkable growth and refinement.

During gestation, neural cells proliferate, migrate and establish connections, setting the foundation for future cognitive, sensory and motor abilities. However, after birth, the brain enters a phase of even more dramatic expansion, characterized by the rapid formation of functional networks that enable infants to interact with and learn from their environment. These processes are crucial for healthy development; disruptions during this time have been linked to long-term risks, including neurodevelopmental disorders such as autism and schizophrenia.

Despite its importance, the birth transition remains poorly understood. While some studies have explored brain development during the fetal and infant stages separately, there is limited detailed knowledge about how the brain’s functional networks emerge and reorganize across this pivotal moment. Questions about the timing, sequence and mechanisms of these changes remain unanswered, leaving gaps in both developmental science and clinical practice. Understanding this process could provide insights into prematurity, prenatal adversity or other environmental influences that shape infant brain development.

Brain regions varied in their speed of development

Led by NYU researchers Dr. Lanxin Ji, a postdoctoral research fellow, and Dr. Moriah Thomason, the Barakett Associate Professor of Child and Adolescent Psychiatry, the team analyzed brain imaging data from 140 individuals, spanning 203 functional MRI (fMRI) scans. These scans covered a developmental range from 25 to 55 weeks of gestational age, including 126 fetal scans and 58 infant scans.

The study used advanced imaging techniques to examine resting-state functional connectivity (RSFC), which measures how different brain regions communicate when the brain is at rest. The team created a brain atlas that divided the brain into 195 functional regions across 8 major networks. Using this framework, they tracked how connections within and between these networks changed over time.

Ji and Thomason observed that RSFC exhibited significant, age-related changes across the 25–55 week gestational age range. The birth transition triggered a rapid surge in functional connectivity on a global scale, and they saw a large jump in these connections at birth, noting distinct growth patterns in different regions. Regions across the subcortical network, superior frontal network and connections between the left and right sides of the brain underwent intense reorganization.

However, these changes were not uniform across the brain. Some connections were seen to exhibit a reverse U-shaped pattern, peaking at around 30 weeks during the fetal stage and then decreasing slightly before birth. Other regions only had minimal changes.

Fetal and infant brain changes are different

Before birth, connections grew the most in the visual and cerebellar areas, which are involved in seeing and movement. However, after birth, changes were strongest in areas controlling movement, vision and planning – the sensorimotor, cerebellar and frontal regions.

In certain areas, the changes could be observed throughout both the fetal and infant stages, yet in others, they grew differently depending on what developmental stage they were in.

Brain efficiency improved over time. Connections across the whole brain – global efficiency – improved in some areas, like motor and parietal regions. Local efficiency – how well nearby areas work together – increased especially in the thalamus, which is crucial for relaying information.

Designing interventions for at-risk infants

"Our results demonstrate a rapid surge in functional connectivity at birth on a global scale, probably reflecting neural processes that support the brain’s transition to the external world," the authors said.

The study raises important questions about how external factors, such as a baby’s sex, premature birth or exposure to prenatal adversity, might influence these developmental trajectories. Premature infants may experience disrupted connectivity patterns, which could affect their long-term cognitive and motor development. Similarly, environmental stressors during pregnancy might alter the timing or efficiency of network growth, potentially increasing the risk of developmental disorders.

By providing a baseline understanding of typical brain development across the perinatal period, these findings offer a framework for designing interventions tailored to at-risk infants.

“This work lays the foundation for future work regarding the maturational timing of brain functional networks spanning the perinatal period,” the authors added.

With deeper knowledge, researchers and clinicians can better understand the origins of developmental challenges and work toward strategies that support healthy brain growth during this critical period of life. 

Reference: Ji L, Menu I, Majbri A, Bhatia T, Trentacosta CJ, Thomason ME. Trajectories of human brain functional connectome maturation across the birth transition. PLOS Biology. 2024. doi: 10.1371/journal. pbio.3002909

This article is a rework of a press release issued by the PLOS. Material has been edited for length and content.