How prenatal stress and early birth affect the baby's brain
Being born early and being exposed to maternal stress before birth both reduce the functional connections between the amygdala and other key brain regions in newborns.
Source
Prenatal stress alters amygdala functional connectivity in preterm neonates
Study at a glance
- Design
- Cohort — Neonatal rs-fMRI amygdala connectivity; Cohort 1 very preterm vs term; Cohort 2 extremely preterm with chart-review prenatal stress
- N
- N=37 · Cohort 1: 12 preterm and 25 term; Cohort 2 extremely preterm enrolled 2012–2015 (exploratory)
- Population
- Very/extremely preterm neonates and healthy term controls
- Outcome
- Amygdala functional connectivity associated with prenatal maternal stress and preterm birth
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How prenatal stress and early birth affect the baby's brain
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12 preterm infants
This cohort has been previously published (, ) and includes 25 term controls and 12 preterm neonates.
10 extremely preterm infants
Twenty eight extremely preterm neonates met all inclusion criteria, and data from 10 extremely preterm neonates with prenatal stress exposure and 16 extremely preterm neonates with no stress exposure were analyzed after exclusion of 2 neonates due to motion artifact.
What they did
The researchers used resting-state functional MRI to study amygdala connections in different groups of newborn babies. In one group, they compared 12 very preterm infants scanned at term-equivalent age to 25 healthy full-term infants. In another group, they compared 10 extremely preterm infants whose mothers had a documented clinical diagnosis of anxiety or depression during pregnancy to 16 extremely preterm infants without this exposure.
What they found
Preterm infants showed weaker connections between the amygdala and subcortical areas like the brainstem, thalamus, and hypothalamus compared to full-term infants. Similarly, among extremely preterm infants, those exposed to prenatal maternal stress had even weaker amygdala connections to these same subcortical areas. Combining the groups suggested a cumulative effect where preterm infants exposed to prenatal stress exhibited the lowest overall amygdala connectivity.
The limits
What it doesn't show
This study cannot establish a direct causal link between maternal stress and altered brain connectivity, nor can it separate the biological effects of stress from maternal anxiety or depression. The researchers relied on retrospective medical chart reviews to identify stress, meaning they may have missed undocumented stressors or mothers with untreated symptoms. Finally, because the cohorts were scanned on different MRI machines at different gestational ages, combining them is only exploratory and could be confounded by scanner-related imaging differences.
Key terms
- amygdala
- A subcortical brain structure critical for processing emotions, social information, and stress responses.
- functional connectivity
- A measure of how closely the activity patterns of different brain regions synchronize with each other over time.
- preterm birth
- Birth that occurs before 37 weeks of pregnancy is completed.
- term equivalent age
- The age at which a prematurely born baby reaches the timeline of a normal full-term birth, usually 40–44 weeks postmenstrual age.
- resting-state fMRI
- A neuroimaging method used to evaluate brain activity and regional interactions when a subject is not performing a specific task.
- subcortical regions
- Groups of diverse neural structures deep within the brain, lying beneath the cerebral cortex, that assist in sensory, motor, and emotional processing.
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Quiz yourself
Across all neonatal study groups, what general pattern of functional connectivity does the amygdala display with subcortical and cortical structures?
Common questions
How was maternal stress measured in this study?
The researchers used a binary classification based on retrospective electronic medical chart reviews, identifying stress exposure if the mother had a documented physician's diagnosis of depression or anxiety during pregnancy.
Did the babies need to be sedated during the brain scans?
No, the babies were scanned without sedation using a 'feed-and-wrap' protocol where they were fed, bundled, and allowed to fall asleep naturally before entering the scanner.
Why is the amygdala the main focus of this research?
The amygdala is central to emotional processing and the stress response, and previous studies in older children and animals have shown it is highly vulnerable to early-life and prenatal stress.
Could the differences in baby movement during the scans explain the results?
No, the researchers carefully measured frame-to-frame movement and found no significant differences in motion between the groups, ensuring that head movement did not bias the connectivity findings.
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