Swedish study highlights rising refusal of vitamin K shot linked to increased bleeding risk in newborns

A large-scale Swedish study reveals that declining vitamin K injections at birth have led to a notable increase in bleeding, including brain haemorrhages, among infants, prompting calls for enhanced parental information and further research.

A large Swedish study published in JAMA Pediatrics has strengthened the case for giving newborns vitamin K shortly after birth, finding that babies who did not receive the injection faced a higher risk of bleeding, including bleeding in the brain, during the first months of life. The findings come from an analysis of more than two million infants born in Sweden between 2003 and 2021, a scale that gives unusual weight to the results.

Vitamin K is central to normal blood clotting, and babies begin life with very limited stores of it. According to paediatric guidance from Stanford Medicine and advice published by HealthyChildren, infants receive only small amounts from their mothers before birth, while breast milk contains little of the nutrient and the newborn gut is not yet making enough of it. That is why the injection is routinely offered in many countries soon after delivery.

The Swedish researchers found that refusal of the shot, while still uncommon, became more frequent over time. They reported that 0.66% of babies did not receive it in 2006, rising to 1.5% in 2021. Infants who missed the injection had around a 50% higher risk of bleeding in the first six months of life, while the risk of intracranial haemorrhage was almost three times higher than among babies who received the dose.

The study also found that oral vitamin K was less protective than the injection. In some cases it is used when parents decline the shot or when a baby has a particular medical reason, but the researchers said the need for repeated dosing over several weeks may make it easier for protection to slip. A Cochrane review has similarly concluded that a single intramuscular dose significantly reduces classic haemorrhagic disease of the newborn, while the American Academy of Pediatrics has long supported routine prophylaxis to prevent serious bleeding in infants.

Researchers said the results reinforce what earlier evidence has already suggested: that vitamin K at birth remains one of the simplest and most effective ways to prevent dangerous bleeding in newborns. They also called for better information for parents and carers, as well as further research into why some families choose to turn it down.