Newborns who missed vitamin K had higher odds of intracranial bleeding

Design

Nationwide register-based cohort

Population

2,020,302 live births at 35 weeks or later in Sweden, 2003-2021

Primary outcome

Bleeding diagnosis within 6 months

Effect

Any bleeding aOR 1.52 (1.27-1.81); intracranial aOR 2.91 (2.13-3.96)

This Swedish nationwide cohort followed 2,020,302 infants born at 35 weeks or later between 2003 and 2021 to six months of age. Of them, 24,089 had no record of intramuscular vitamin K at birth. The proportion fell to 0.66% in 2006, then more than doubled to 1.50% by 2021.

Infants who did not receive vitamin K had higher odds of any bleeding diagnosis (aOR 1.52, 95% CI 1.27 to 1.81) and of intracranial bleeding (aOR 2.91, 2.13 to 3.96) than those who did.

The data are observational, and families who decline vitamin K may differ in other ways. But the direction matches the well-understood biology of vitamin K deficiency bleeding, and refusal is rising in several countries.

• Give intramuscular vitamin K to every newborn at birth.
• When parents hesitate, explain that late bleeding can be intracranial and occurs without warning.
• If intramuscular vitamin K is refused, document the discussion and offer an oral regimen as a less effective alternative.
• Consider vitamin K deficiency bleeding in any young infant with unexplained bruising, bleeding or irritability.

Why it matters

Refusal is rising in countries with long-established programmes, and the consequence is brain haemorrhage in infants.

Don't overread it

Some infants may have received vitamin K without a record, and families who decline may differ in other ways.

The statistics, in plain English

An adjusted odds ratio of 2.91 means intracranial bleeding was nearly three times as likely in infants without recorded vitamin K. Because intracranial bleeding in infancy is uncommon, the absolute risk remains small, but the harm when it happens is severe.

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