Vitamin C supplementation during pregnancy may be linked to aspects of an infant’s emotional development, according to new research examining how maternal stress, nutrition and early temperament interact.
Researchers followed 302 pregnant participants and later assessed their babies at around 6 months of age. They found that higher levels of maternal depression, anxiety and stress during pregnancy were associated with greater negative affect in infants, a temperament pattern that can include increased fussiness, distress and difficulty being soothed.
Intriguingly, reported use of vitamin C supplements during pregnancy statistically accounted for a small part of that relationship.
According to the study published in Developmental Psychology, prenatal vitamin C supplementation, but not vitamin C obtained through diet, showed a significant mediation effect between maternal prenatal distress and infant negative affect.
The findings suggest a possible role for maternal nutrition in early socioemotional development, but they do not prove that taking extra vitamin C during pregnancy will make babies calmer or prevent later mental-health problems.
Table of Contents
Researchers Followed More Than 300 Pregnancies
The study included 302 pregnant participants, with an average maternal age of about 32 years.
Researchers collected information on both mental health and nutrition during pregnancy.
Maternal psychological distress was assessed using established measures covering:
- depression;
- anxiety; and
- perceived stress.
Researchers also assessed vitamin C exposure in two different ways.
Participants reported their use of vitamin C-containing supplements, while trained research staff conducted multiple 24-hour dietary recalls to estimate how much vitamin C participants were obtaining from food.
At approximately 6 months after birth, caregivers completed the Infant Behaviour Questionnaire-Revised, a standardized tool used to assess aspects of infant temperament.
| Study Detail | Finding |
|---|---|
| Pregnant participants | 302 |
| Average maternal age | About 32 years |
| Infant assessment age | Around 6 months |
| Maternal factors studied | Depression, anxiety and stress |
| Nutrient studied | Vitamin C |
| Sources assessed | Supplements and diet |
| Infant outcome | Negative affect |
| Journal | Developmental Psychology |
| Published | 2 November 2026 |
What Is ‘Negative Affect’ in an Infant?
Negative affect does not mean a baby has a mental-health disorder.
It is a temperament characteristic describing a tendency to experience and express emotions such as distress, frustration, sadness or fear more readily.
Infants with higher negative-affect scores may, for example, become upset more easily or take longer to settle after becoming distressed.
Temperament varies normally between babies.
However, researchers study negative affect because higher levels early in life have been associated in some studies with later emotional and behavioural outcomes.
The current research measured temperament at only 6 months of age, so it cannot determine whether the infants will later develop anxiety, depression or another psychiatric condition.
Higher Pregnancy Distress Was Linked to Infant Temperament
The clearest result involved maternal psychological distress.
Higher levels of depression, anxiety and stress during pregnancy predicted higher negative affect in infants at 6 months.
The standardized association was approximately β = 0.21, indicating a measurable but not overwhelming relationship.
This fits with broader research suggesting that the prenatal environment can influence fetal development, including systems involved in stress regulation and behaviour.
However, the study remains observational.
It cannot prove that maternal distress directly caused the differences seen in infant temperament.
Vitamin C Supplements Showed a Small Association
Researchers then examined whether vitamin C could help explain part of that relationship.
They found that reported vitamin C supplementation during pregnancy produced a statistically significant indirect effect.
The mediation effect was approximately β = 0.02, with a bootstrapped confidence interval that did not cross zero.
That effect is small.
It nevertheless suggests that supplement use may account for a modest portion of the relationship between maternal prenatal distress and infant negative affect.
The Oregon Health & Science University report on the research describes nutrition as a potentially modifiable factor that could eventually become part of strategies aimed at supporting fetal brain development.
Vitamin C From Food Did Not Show the Same Result
One of the most notable findings was the difference between supplements and dietary vitamin C.
Researchers estimated food-based vitamin C intake using repeated dietary recalls.
Unlike supplemental vitamin C, dietary vitamin C intake did not significantly mediate the association between maternal distress and infant negative affect.
The study does not establish why.
Possible explanations could include differences in consistency of intake, dosage, measurement accuracy or other characteristics of people who use supplements.
Because this was not a randomized experiment, researchers cannot conclude that supplements are inherently more effective than vitamin C-rich foods for infant emotional development.
Why Vitamin C Could Matter During Pregnancy
Vitamin C is an essential nutrient with several important biological functions.
It contributes to:
- antioxidant defense;
- collagen synthesis;
- neurotransmitter-related processes;
- enzyme activity; and
- normal tissue development.
It also helps protect cells from oxidative stress.
Pregnancy increases nutritional demands because nutrients support both maternal health and fetal development.
Researchers are particularly interested in vitamin C because psychological stress can influence eating patterns and nutritional status.
According to OHSU, about one-quarter of pregnant women in the United States may consume less vitamin C than recommended, making nutritional adequacy an important area of prenatal research.
Could Vitamin C Protect the Developing Brain From Stress?
That is one hypothesis raised by the study, but it has not yet been proven.
Vitamin C has antioxidant properties and participates in biological systems involved in stress regulation.
Researchers therefore propose that adequate vitamin C could potentially influence the intrauterine environment during periods of maternal psychological stress.
But the present study did not directly demonstrate a mechanism in the fetal brain.
It identified a statistical relationship between supplement use, maternal distress and later infant temperament.
Further experimental research would be necessary to establish how vitamin C might influence neurodevelopment.
This Was Not a Randomized Vitamin C Trial
This is the most important limitation.
Participants were not randomly assigned to take vitamin C or a placebo.
Instead, researchers observed supplement use that was already occurring.
People who choose to use supplements can differ from non-users in many ways.
They may differ in:
- diet quality;
- income;
- education;
- prenatal healthcare;
- health awareness;
- overall supplement use; and
- other lifestyle factors.
Statistical models can account for some of these differences, but they cannot eliminate every possible confounding factor.
For that reason, the study supports an association, not proof of cause and effect.
Researchers Relied on Parent-Reported Infant Temperament
Another limitation is the way infant emotional behaviour was measured.
Caregivers completed a standardized questionnaire about their babies.
This is an established research method, but parent reports can be influenced by personal perceptions, stress levels and interpretation of a child’s behaviour.
Future research incorporating direct behavioural observations or physiological measurements could provide additional evidence.
Does the Study Show Vitamin C Prevents Mental-Health Disorders?
No.
The infants were assessed at approximately 6 months old.
The researchers did not diagnose depression, anxiety, ADHD or other psychiatric conditions.
Negative affect is a temperament characteristic and can be associated with later developmental outcomes, but it is not itself a psychiatric diagnosis.
The research team plans to continue following the children as they grow to examine whether early differences persist or relate to later clinical outcomes.
Until that longer-term evidence is available, claims that prenatal vitamin C prevents childhood mental-health disorders would be premature.
Should Pregnant Women Take Extra Vitamin C?
The study should not be interpreted as evidence that every pregnant person should begin taking high-dose vitamin C.
Pregnancy already involves established nutritional recommendations, and many prenatal vitamins contain vitamin C.
Individual requirements can vary depending on diet, health status and other supplements.
More is also not necessarily better.
The current research does not establish an optimal vitamin C dose for infant emotional development.
Pregnant people considering changes to supplements should therefore discuss them with their healthcare professional, particularly if they are already taking a prenatal multivitamin.
Why the Findings Still Matter
Despite these limitations, the study highlights an important research direction.
Psychological distress during pregnancy can arise from complex circumstances that are often difficult to modify quickly.
Nutrition may sometimes be more amenable to intervention.
If future randomized trials confirm that specific nutritional strategies can reduce some developmental effects associated with prenatal stress, relatively inexpensive interventions could potentially complement broader maternal mental-health and prenatal-care programs.
OHSU researchers say their wider goal is to improve access to nutritional counseling and healthy foods during pregnancy while continuing to study which interventions provide measurable benefits.
What Comes Next?
The strongest next step would be controlled research capable of testing causality.
Researchers would need to determine:
- whether vitamin C supplementation itself produces measurable changes in infant temperament;
- which pregnant populations benefit most;
- the optimal dose and timing;
- whether benefits persist beyond infancy; and
- whether any differences translate into meaningful long-term developmental outcomes.
For now, the study provides an intriguing connection between maternal distress, prenatal nutrition and infant emotional development.
The most defensible conclusion is not that vitamin C makes babies emotionally healthier, but that prenatal vitamin C supplementation was associated with a small reduction in the relationship between maternal distress and negative affect at 6 months.
That finding now needs to be tested in studies specifically designed to determine whether vitamin C itself is responsible.
