Early detection of vitamin B12 deficiency in breastfed newborns
What it found
In 12 exclusively breastfed infants with vitamin B12 deficiency, early treatment with a vitamin B12 injection normalised metabolic markers and all remained healthy at one year.
The deficiency came from their mothers, most of whom ate vegetarian diets or had absorption problems.
What they found
Studies in people
Metabolic markers at first visit
All 12 infants had very low serum vitamin B12 (below 100 pg/mL) and very high levels of total homocysteine (average 71.2 µM). Urine methylmalonic acid was also very high.
Treatment and outcome
A single intramuscular injection of 1.0 mg hydroxocobalamin quickly normalised the metabolic abnormalities. At a mean age of one year, all infants were symptom-free with normal marker levels.
Mothers' vitamin B12 status
All mothers had low vitamin B12 (average 137.5 pg/mL) and high homocysteine (average 18.3 µM). Nine followed a strict vegetarian diet, one had malabsorption after bariatric surgery, one had pernicious anaemia, and one had multiple deficiencies.
Anaemia in infants
Four infants had temporary anaemia with slightly low haemoglobin (9.3 to 10.6 g/dL), but no megaloblastic anaemia was found in any infant.
Maternal B12 and birth outcomes
The mothers' vitamin B12 levels were not linked to birth weight or gestational age at birth in this group.
What the authors conclude
“In our study, early detection through NBS may have prevented hematological abnormalities and irreversible neurological damage in infants with acquired vitamin B12 deficiency due to maternal vitamin B12 deficiency.”
Also in their conclusions
- They conclude that early detection through newborn screening may have prevented blood problems and irreversible neurological damage in these infants.
- They advise screening for maternal vitamin B12 deficiency throughout pregnancy and asking women about diet and medical history to spot those at risk.
- They say healthcare providers should not rely only on serum vitamin B12 but also check functional markers like methylmalonic acid and homocysteine.
How it was done
The authors wanted to see whether finding and treating vitamin B12 deficiency early in babies could prevent lasting neurological damage, anaemia and poor growth. They also wanted to highlight the importance of checking vitamin B12 levels during pregnancy.
They looked back at the records of 12 newborns (5 boys) aged 1 to 2 months who were exclusively breastfed and had no symptoms but were referred because newborn screening showed high methylmalonic acid or homocysteine. They collected data on the mothers' diets, health and vitamin B12 levels, and followed the infants' metabolic markers after treatment.
What it can’t tell you
- This was a small study of 12 infants, so the results may not apply to all babies.
- It cannot prove that early treatment prevented neurological damage, only that the infants remained healthy.
- It cannot show whether the same approach would work in other populations or with different treatment plans.
Who paid
- Conflicts
- The authors declare no conflict of interest.
- Authors work at
- Santa Maria's Hospital-Lisbon North University Hospital Center, Portugal; University of Lisbon, Portugal; National Institute of Health Dr Ricardo Jorge, Portugal
The paper
- Title
- Acquired Vitamin B12 Deficiency in Newborns: Positive Impact on Newborn Health through Early Detection
- Type
- Study
- Evidence
- Studies in people
- Summarised from
- Full text
- Cite
- Lipari Pinto P, Florindo C, Janeiro P, et al (2022). Acquired Vitamin B12 Deficiency in Newborns: Positive Impact on Newborn Health through Early Detection. Nutrients. doi:10.3390/nu14204397Free full textPubMed 36297083DOI
Summary written 26 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error