Even Mild Anaemia in Pregnancy Linked to Smaller Brain Volume in Babies, Study Finds
Babies born to mothers with even mild anaemia during pregnancy have smaller brains than those born to non-anaemic mothers, with differences concentrated in regions governing movement, learning, and emotion regulation, according to a study published September 9, 2026, in the journal Brain Communications (The Guardian).
The research, led by Jessica Ringshaw of King's College London's Institute of Psychiatry, Psychology & Neuroscience (IoPPN) and the University of Cape Town, followed more than 300 mother-infant pairs in Cape Town, scanning the infants' brains multiple times between three months and two years of age. Total brain volume in babies born to anaemic mothers averaged 4% lower than in those born to non-anaemic mothers, despite the anaemic mothers presenting with only mild forms of the condition. Anaemia, in this context, refers to a shortage of healthy red blood cells or haemoglobin, the protein that carries oxygen around the body — meaning the developing fetus may receive less oxygen than it needs.
The structural brain differences were found in three areas: the putamen and caudate nucleus (both part of the basal ganglia, deep-brain structures involved in movement and learning), and the corpus callosum, the bundle of nerve fibres connecting the brain's two hemispheres. These disparities were not detectable at the earliest scanning time points. They first appeared at age one and widened over the second year of life. The corpus callosum was approximately 4% smaller at 12 months in the maternal-anaemia group and roughly 6% smaller by 24 months, suggesting a developmental trajectory that increasingly diverges rather than a fixed gap present from birth.
The study used cheaper, more portable MRI scanners than conventional hospital machines, a methodological choice that broadens the feasibility of long-term brain imaging in low-resource settings where anaemia prevalence is highest. The researchers also recorded higher rates of anaemia among women living with HIV, reinforcing the intersection of infectious disease burden and nutritional deficiency in shaping fetal brain development.
These findings arrive within a growing body of evidence linking maternal anaemia during pregnancy to altered child brain development. A 2025 neuroimaging sub-study by Ringshaw and colleagues, published in BMC Medicine, had previously associated antenatal maternal anaemia with smaller child brain volumes of the corpus callosum and caudate, structures also implicated in the current Brain Communications paper. An earlier 2022 cohort study by Wedderburn et al. in JAMA Network Open found that anaemia in pregnancy was associated with altered child brain structural development among children assessed at age two. Notably, that 2022 study found that child anaemia itself was not associated with brain volumes, nor did it mediate the link between maternal anaemia during pregnancy and brain volumes, pointing to the environment in the womb as the operative mechanism rather than the child's own nutritional status after birth (JAMA Network Open; PubMed).
Research from the Karolinska Institutet has further connected early maternal anaemia to increased risk of autism, ADHD, and intellectual disability in offspring, adding clinical and behavioural outcomes to the structural brain imaging data (Karolinska Institutet).
The broader context here is one of scale and tractability. Maternal anaemia affects hundreds of millions of women globally, concentrated in low- and middle-income countries where iron deficiency, infectious disease, and limited antenatal care converge. The finding that even mild maternal anaemia produces measurable, trajectory-diverging brain structure differences reframes the condition from a routine blood-test marker to a neurodevelopmental risk factor with potential lifelong consequences. The progressive widening of the gap between 12 and 24 months is particularly consequential for intervention design, as it implies that the window for mitigation may extend beyond the prenatal period into early postnatal life.
The use of portable MRI technology also raises questions about translational potential. If structural brain differences can be tracked over time in resource-limited settings using lower-cost imaging, the methodology could support large-scale cohort monitoring in populations where conventional neuroimaging infrastructure is absent, potentially informing iron supplementation and antenatal care policies at a population level. Whether the observed volumetric differences translate into detectable cognitive or behavioural outcomes in this cohort will require longer follow-up, but the converging evidence from the Karolinska epidemiological data and the Wedderburn et al. structural findings provides a strong prior.
What remains unresolved is whether iron supplementation or other antenatal interventions can reverse or attenuate the developmental trajectory once structural divergence is established. The 2022 finding that postnatal child anaemia did not mediate the maternal-pregnancy effect on brain volumes suggests that addressing postnatal iron status alone may be insufficient, placing the burden of prevention firmly on the antenatal period.
